One is on here.
Andrew Geraci, Northwestern: Okay, is that good.
Christian Boutan: Yes.
Andrew Geraci, Northwestern: Okay, great.
Andrew Geraci, Northwestern: Okay yeah well, thanks to the organizers for inviting me to give you an update on the Ariadne accion experiment it's great to see everyone virtually and, of course, it would be better to.
Andrew Geraci, Northwestern: be able to chat in person, but it's certainly good to at least get together and some kind of format, and so, most of the.
Andrew Geraci, Northwestern: experiments and ideas that we've heard about so far have been sort of in this group, where we're looking for the accion as a dark matter candidate.
Andrew Geraci, Northwestern: let's see are my slides not working here okay.
Andrew Geraci, Northwestern: And, and of course the I won't spend any time at this meeting motivating the importance of searching for the accion our experiment is a little different in the sense that it is a.
Andrew Geraci, Northwestern: Taking advantage of the fact that the accion can actually mediate a.
Andrew Geraci, Northwestern: Short range interaction between nucleotides and so we're looking for sort of spin dependent fifth force that will only turn on between two objects, when you get them.
Andrew Geraci, Northwestern: close enough within the rain set by the compton wavelength, of the accion, and this has the additional virtue that we're actually essentially looking for the accion.
Andrew Geraci, Northwestern: The QC dx on itself rather than necessarily the axon as the as the background field that's that's.
Andrew Geraci, Northwestern: Forming dark matter, and so in this case we don't need to depend on any cosmological assumptions in order to do the search for the accion.
Andrew Geraci, Northwestern: So our experiment is collaboration between our group at northwestern as well as folks at perimeter institute Stanford indiana university CAP in Korea Chris and and ptb so.
Andrew Geraci, Northwestern: If we look at the parameter space for the accion, in particular the QC D accion.
Andrew Geraci, Northwestern: it's it's convenient because, since the coupling is is inversely proportional to the mass we can basically think about it as a one parameter range here to premiere tries to the allowed space for the QC accion so here is a plot that i've borrowed from a.
Andrew Geraci, Northwestern: particle data group plot from a few years ago where we're basically it's laid out some of the astrophysical balance and.
Andrew Geraci, Northwestern: And hints as well as the current experiments and and and experimental bounds, and so.
Andrew Geraci, Northwestern: So basically the accion needs to be lighter than sort of 10 me vs due to astrophysics and depending on the model of cosmology whether or not you have.
Andrew Geraci, Northwestern: hi Andrew scale of inflation or not, the accion may be disfavored if it's lighter than, say micro electron volts.
Andrew Geraci, Northwestern: So, most of the experimental bounds from the HALO scope experiments are at the sort of micro to 10 micro ev range and particular has been quite a lot of exciting activity.
Andrew Geraci, Northwestern: going on here over the past several years by now several players from many different countries who are contributing towards closing in on getting down to the projected.
Andrew Geraci, Northwestern: sensitivity lines for the accion photon coupling in this exciting range here at the micro ev to 10s of micro review range and there are a number of exciting new experiments that are also coming on line shortly.
Andrew Geraci, Northwestern: In some form of development to search for lower frequency accion using lumped element type searches the casper experiment is also able to look for accion that are extremely light.
Andrew Geraci, Northwestern: Our experiment, along with the mad Max experiment is aiming at targeting the higher mass range of the accion here above the range where the.
Andrew Geraci, Northwestern: A dmx and those type HALO scopes can operate and then potentially closing up all the way to were cast and jaso are able to probe at higher masses.
Andrew Geraci, Northwestern: So the idea would be to sort of close up the higher end of the traditional accion window, so, if I can put Ariadne and context and some of the other.
Andrew Geraci, Northwestern: Experiments, most of which we've heard about, some of which we're still going to hear about it this workshop, you can sort of characterize things by.
Andrew Geraci, Northwestern: By the source and the coupling and so, as I was saying, the vast majority of the efforts that are ongoing and planned are looking for a background of cosmic accion, namely the dark matter accion and the majority of those experiments are.
Andrew Geraci, Northwestern: intending to search for the axon coupling two photons the casper experiment is which will hear about later is going to look for X and coupling two nucleotides.
Andrew Geraci, Northwestern: The cracks experiment which we're also going to hear about at this workshop is looking at potentially detecting couplings a dark matter accion still electrons.
Andrew Geraci, Northwestern: The cast and future plan jaco experiment will look for solar axons as opposed to dark matter axons but looking for the coupling the photons.
Andrew Geraci, Northwestern: And then there's the final class of experiments which are, which is the group that area and he belongs to, where there are lab produced accion and we heard about the exciting developments in the light shining through walls experiments at daisy yesterday Ariadne is looking for a coupling.
Andrew Geraci, Northwestern: company have accented nucleotides in the lab produced way where the accion is actually going to be the the virtual force carrier in a short range.
Andrew Geraci, Northwestern: of independent force and and we're particularly targeting the coupling of the QC D accion and so So if I look at.
Andrew Geraci, Northwestern: The accion exchange between two nucleotides there's basically two different terms, I can write down for the vertices.
Andrew Geraci, Northwestern: So, one of which is a scale or a coupling which is is related to data Q CD So here we have something that goes like data QC over.
Andrew Geraci, Northwestern: X and take a constant time some energy scale mew, which is a warder 60 MTV or so.
Andrew Geraci, Northwestern: And then there's also the derivative coupling or pseudo scale or coupling were in the non relativistic limit it looks like the gradient of the axon field dotted into the spin Sigma of.
Andrew Geraci, Northwestern: Firm yeah So if I bring to nuclei together at sufficiently short distance within this content wavelength that accion, then I can produce these types of interactions.
Andrew Geraci, Northwestern: Where the axon is basically the force mediator between the nuclei and so there's basically three classes of interactions that one can one can.
Andrew Geraci, Northwestern: achieve so one is a monopole monopole or coupling one is a monocle dipole coupling and then I could have two copies of the of the spin dependent for text for a dipole dipole coupling.
Andrew Geraci, Northwestern: Our experiment Ariadne is focused on the middle case here, where we're looking for a monopole dipole coupling or, in other words and interaction between the spin of one nucleus in the mass of another.
Andrew Geraci, Northwestern: And so, if I bring to nuclei together at some short distance are there is a potential that I can write down that basically goes like Sigma are so Sigma being the span of one for me on and are the separation distance to the other mass nearby there's a term.
Andrew Geraci, Northwestern: that's exponential here that's describing the range of the interaction This again is given by the content wavelength Lambda of the accion so if you're within that range this potential turns on essentially.
Andrew Geraci, Northwestern: And then, I have a basically a one of our R squared times my coupling Constance so there's a product of the coupling constants here from the vertices the scale of coupling and the dipole coupling.
Andrew Geraci, Northwestern: In this case, and so, because this couples to Sigma and Sigma is proportional to the magnetic moment of nuclear on.
Andrew Geraci, Northwestern: We can think about this as sort of a fictitious magnetic field in some way where the accion field is some background and and field coupling to the magnetic moment.
Andrew Geraci, Northwestern: But it's important to emphasize that this is very different than a regular magnetic field, for example, it doesn't obey maxwell's equations it doesn't.
Andrew Geraci, Northwestern: couple to angular momentum or moving charges and, most importantly, for our experiment it's not screened by magnetic shielding which will be a crucial aspect of the work i'm going to tell you about so.
Andrew Geraci, Northwestern: As I was mentioning the interaction has some finite range and that range is determined by this content wavelength, of the accion which is related to the mass of the accion so.
Andrew Geraci, Northwestern: If I look at the astrophysical limits on the accion mass which constrain it to be less than a few Milli electron volts.
Andrew Geraci, Northwestern: Then this gives me some link scale over which I should start probing to search for these accion media interactions.
Andrew Geraci, Northwestern: And for accion that are lighter than about six MTV then millie electron volts, then the the range tends to be at the 30 micron length scale or higher for for later axioms and so that gives you some sort of target for what sort of distances, you want to look for these forces.
Andrew Geraci, Northwestern: And so the way we're going to do this experiment is to use nuclear magnetic resonance and so here's sort of the cartoon example of the interaction, so we take a.
Andrew Geraci, Northwestern: spin one half nucleus, in this case a helium three nucleus, and we put it in an external magnetic field.
Andrew Geraci, Northwestern: And so, when I when I have this spin one half system in the magnetic field, I get an energy splitting between the spin up and spin down states of the nuclear spin.
Andrew Geraci, Northwestern: With the with the difference here set by the nuclear lahmar procession frequency and so now, if I then come by my.
Andrew Geraci, Northwestern: My my nuclear spin here with a nearby mass, then this mass spin interaction that's mediated by the accion basically acts like an effective fictitious magnetic field that I turn on.
Andrew Geraci, Northwestern: And so I can arrange a situation so that I basically modulate the distance between the mass and the spin and when I do this I create a time very component of that fictitious magnetic field.
Andrew Geraci, Northwestern: And so I arranged situation so there's a basically a transverse component of that time very magnetic field.
Andrew Geraci, Northwestern: Which is actually oscillating back and forth directly at the nuclear longer procession frequency and what this allows me to do is to resident Lee Dr spin per session in the helium three nucleus, where i'm using the accion.
Andrew Geraci, Northwestern: fictitious magnetic field, if you like, as the as the transverse are a field that you'd normally be using say with a coil and then Mr.
Andrew Geraci, Northwestern: And so, this gives you a nice sort of resonant enhancement technique where there's essentially a Q factor that comes into here, which is given by the frequency times the T to or the transverse D coherence time in in the spins.
Andrew Geraci, Northwestern: And so the the geometry of the of the actual experiment looks a little bit more like this, where we don't have to isolated spheres, but rather we have a vessel that contains laser polarized helium three gas.
Andrew Geraci, Northwestern: And then, this vessel is enclosed in a in a block of courts that block of quartz is coated with Nairobi and thin film as a superconducting shield to eliminate regular magnetic fields, from acting on the helium.
Andrew Geraci, Northwestern: And then nearby that nearby that block we bring an source mass and for this, this is a tungsten cylinder that's.
Andrew Geraci, Northwestern: Here are shown as as essentially a gear with teeth in it, and so the idea is that we we spin this this gear in some short distance from the from the helium.
Andrew Geraci, Northwestern: Gas sample and then, as the teeth of this pass by.
Andrew Geraci, Northwestern: We basically modulate the strength of this effective transverse magnetic field, so that when the tooth is near, we have a strong interaction from the accion and when you're in between the teeth and the interaction disappears.
Andrew Geraci, Northwestern: Where it's suppressed by that exponential drop off of the.
Andrew Geraci, Northwestern: The content wavelength, and so, basically, I can apply a periodic signal at the nuclear bomb opposition frequency, which then drives spin per session in the sample of laser polarize helium which can just be checked can be picked up with a with a squid magnetometer.
Andrew Geraci, Northwestern: loop to measure the magnetic field, and so the the limit that we think we're going to ultimately be up against is actually set by the quantum spin projection noise and not sort of the magnetometer noise in this case.
Andrew Geraci, Northwestern: And so, this mega minimum magnetic field, I can see basically goes like one over the square root of the density of spins times the volume times this transverse D coherence time.
Andrew Geraci, Northwestern: Coherence 92 so.
Andrew Geraci, Northwestern: If for for our for our experiment, we can then estimate given given this fundamental limit how sensitive will be in terms of probing for the for the accion.
Andrew Geraci, Northwestern: And so here's a plot of our projected sensitivity, as well as some balance from other previous work with an experiment and astrophysics so on this plot on the.
Andrew Geraci, Northwestern: On the vertical scale, I have the product of these two coupling constants here that we're sensitive to the scale or coupling and the and the dipole coupling to New Orleans for the accion.
Andrew Geraci, Northwestern: And then on the horizontal scale on the top I have them accion mass, so this is going from a few millet ev here on the left, down to micro ev here on the right so it's kind of going backwards.
Andrew Geraci, Northwestern: And in the on the bottom horizontal axis, I have the force range in this in in centimeters so going from cut this 30 micron length scale up to about the links below 10 centimeters.
Andrew Geraci, Northwestern: that the best limits that are derived in the laboratory now are from precision magnetometer experiments that's the shaded blue area here at the top.
Andrew Geraci, Northwestern: If you take the current limits from astrophysics and combine them with the best and that's from experiment on this product, the coupling constants.
Andrew Geraci, Northwestern: You can arrive at this shaded tan area here, which is a few orders of magnitude better than what you can do only by experiment so far.
Andrew Geraci, Northwestern: But in our system, given this resident enhancement technique and the high polarized spin density that we're aiming to achieve.
Andrew Geraci, Northwestern: Depending on our transverse the coherence time T to we we now expect to be able to start to probe into the space where we expect the QC the accion to live on this parameters based, and so the.
Andrew Geraci, Northwestern: The shaded Gray band here tells you sort of where you expect the accion to live.
Andrew Geraci, Northwestern: The upper boundary of the band is set from our limits that we have on the neutron electric dipole moment, so we know theta QC D has to be less than about 10 to the minus 10.
Andrew Geraci, Northwestern: And so, this is setting some some limit on the scale or coupling here the accion.
Andrew Geraci, Northwestern: Also, we have a we have a lower limit where where because there is a certain amount of cpu violation that we already know is present in the standard model.
Andrew Geraci, Northwestern: We expect that data QC will actually be larger than about 10 to 16, and so the accion if it exists, if it has a reason to exist, should be somewhere in this band between this great band here set by David Cassidy between 10 minutes 10 and 10 minutes 16.
Andrew Geraci, Northwestern: So in our in our initial experiment we're hoping to start to carve into that parameter space and then assuming we have systematics and so forth under control we're projecting by scaling up the experiment.
Andrew Geraci, Northwestern: We should be able to carve out something's more similar to this blue line where we're now in the log scale here taking out about half of the parameter space for the accion in this sort of mass range.
Andrew Geraci, Northwestern: If we were limited only by the squid magnetometer than in principle, we could get all the way down to this blue dashed line here at the bottom.
Andrew Geraci, Northwestern: And in order to do this, we would need to take advantage of some techniques for example spin squeezing or some other mechanism to get over the the spin projection noise.
Andrew Geraci, Northwestern: So, but at least for the initial experiment we're starting to just start to carve into this range we're actually sensitive to interaction that would be at the strength predicted for the QC dx and within this allowed band, so this is a plot showing the kind of the inner.
Andrew Geraci, Northwestern: Inner vacuum can of the of the experiment here rendered in a in a drawing so we have we have three helium three sample chambers that surround.
Andrew Geraci, Northwestern: Our source mass, which is a tungsten rotor, this is a prototype we have here of the.
Andrew Geraci, Northwestern: Of the rotor it's about 373 820 centimeters diameter and it has teeth cut out here to create this modulation in the accion magnetic field as it spins.
Andrew Geraci, Northwestern: And so, if I if I look down from a top down view here on the right image at the at the.
Andrew Geraci, Northwestern: interface between the source mass and the in the courts block where the helium is there's a very narrow.
Andrew Geraci, Northwestern: gap here about 50 micron gap between the two, and then the spinning wheel, as it turns basically modulates that accion fictitious magnetic field.
Andrew Geraci, Northwestern: So for our for our case we're using a tungsten mass to get a high nuclear density this wheel has 11 segments in it and it spins at a frequency of about nine hertz.
Andrew Geraci, Northwestern: Which which corresponds to about 100 hertz for the nuclear spin procession frequency the sample volume for our initial experiment is three by three millimeters by 150 microns and we're targeting kind of accion in the range of separations about 200 to 300 microns or so.
Andrew Geraci, Northwestern: So, to get the the helium hyper polarized it's difficult to use ordinary magnetic fields just due to the boltzmann boltzmann factor, and so we use optical pumping techniques in particular.
Andrew Geraci, Northwestern: Our collaborators at indiana university are have developed expertise in Meta stability exchange optical pumping.
Andrew Geraci, Northwestern: And so the idea is you basically take helium and by rf discharge can excited into some Meta stable state.
Andrew Geraci, Northwestern: And then from this date, you can optically pump it using 1083 nanometre light and then through collisions you wind up re polarizing the ground state, and you can produce a polarization is on the order of.
Andrew Geraci, Northwestern: 50 to 70% in relatively short time scales on timescales of seconds.
Andrew Geraci, Northwestern: So this has been developed at the in the laboratory in indiana now for quite a while we've recently installed the system on top of.
Andrew Geraci, Northwestern: Tests cryostat down there where you can see kind of the timescale from our initial turn on that system now on the on the first test Christ at their.
Andrew Geraci, Northwestern: Where we're getting something on the order of 30% polarization polarization in the matter in the matter of a few seconds, so this is good for for keeping a high efficiency and duty cycle and the experiment, to be able to polarize the helium this on this quick timescale.
Andrew Geraci, Northwestern: So in this experiment in order to get the sensitivity that we advertise and to get down to the QC de accion sensitivity range, we have to contend with a number of experimental.
Andrew Geraci, Northwestern: background sources and noise in the experiment, so this is a list of some of the things that we're worried about.
Andrew Geraci, Northwestern: i'm not going to go over all of these things in for this audience here, but I want to at least say a little bit about a few of them that were most recently working on investigating in particular.
Andrew Geraci, Northwestern: The issues of challenges with magnetic keeping medic gradients to a minimum.
Andrew Geraci, Northwestern: worrying about things like vibration of our of our mass and then also effects that have to do with magnetic backgrounds.
Andrew Geraci, Northwestern: From magnetic noise sources, for example, Johnson noise due to thermal motion of electrons and materials producing magnetic field noise.
Andrew Geraci, Northwestern: The barnett effect which is basically the mechanization of an object that occurs when you rotate it if you have a paramedic object, as well as things like magnetic impurities.
Andrew Geraci, Northwestern: So one of the one of the issues for us in Ariadne is, we want to have the entire volume of a sample respond to this.
Andrew Geraci, Northwestern: fictitious accion magnetic field in order for that to happen, we want basically the entire.
Andrew Geraci, Northwestern: sample to be to be on resonance and so, so we, we have to essentially figure out a way to eliminate gradients and the magnetic field, which would, which would cause a spread in the alarm or frequency of the nuclei in our in our sample.
Andrew Geraci, Northwestern: And this, this is a little bit at odds with the with the with the need that we have to have a superconducting magnetic shield very close to the to the to the sensor.
Andrew Geraci, Northwestern: And so we need the superconducting magnetic field to avoid Johnson noise essentially So if you have a material, like, for example in a regular magnetic.
Andrew Geraci, Northwestern: metal or some other sort of magnetic shield then there's some thermal notion of the electrons and the surface of the material.
Andrew Geraci, Northwestern: This creates a fluctuating magnetic field spectrum, which would be larger than the the field that we're trying to measure from from the accion, and so we really need a superconducting shield to eliminate this.
Andrew Geraci, Northwestern: The super interesting shield works and the principal the Meissner effect so you can't have flux penetrating across a super noting boundary.
Andrew Geraci, Northwestern: And mathematically it's easy to think about the situation in our experiment, where we have an ensemble of dipole so the polarized nuclear nuclear.
Andrew Geraci, Northwestern: helium three spins right up against a superconducting boundary, so we need the boundary to be very close because we're trying to measure these really short range interactions.
Andrew Geraci, Northwestern: And so, if you have a polarized spin say up against a supercritical boundary you can think about it sort of in this method of images, where, if I have a dipole.
Andrew Geraci, Northwestern: With an image across the boundary then, if I were to draw the field lines coming out of the dipole, then we would satisfy that condition that the flux would cancel and there'd be no flux across across the boundary.
Andrew Geraci, Northwestern: So why is this a problem, so if we if we take the we take the helium and we arrange it in a.
Andrew Geraci, Northwestern: In a sphere Royal configurations of a sphere, or a sphere road has a nice feature that the magnetic field is consonant side for for uniformly magnetized sphere or sphere right.
Andrew Geraci, Northwestern: But then I take that that sphere right and I place it up against a boundary now, I have to worry about the magnetic field that's produced from the image dipole, if you like, across the boundary.
Andrew Geraci, Northwestern: And so, this magnetic field outside the spherical region is not uniform, of course, it looks like a dipole.
Andrew Geraci, Northwestern: And therefore now, this will spoil the uniformity of the of the magnetic field so so in order to get the constant interior field, we have to worry about this.
Andrew Geraci, Northwestern: This perturbation that's caused by this image sphere road which then is going to cause a variation in the nuclear lumber procession frequency.
Andrew Geraci, Northwestern: But this is an issue because we wanted to take advantage of the full sensitivity to drive the entire sample on resonance.
Andrew Geraci, Northwestern: And so to do this, we can create a compensation method where we we use a simple symmetrically placed coil which can essentially.
Andrew Geraci, Northwestern: flatten out that the field at the central region where the sample is, and so, by doing this with appropriate choice of current and and positioning of the coil we can essentially.
Andrew Geraci, Northwestern: fill in, if you like, the gradient from that from from the from the image dipole and make the field.
Andrew Geraci, Northwestern: About 100 times flatter over the samples central area here, and so this this will allow us fan to take advantage of this really high tea two times that we could achieve in the systems and exceeding here 100 seconds in principle.
Andrew Geraci, Northwestern: So another challenge thats related to the fact that we're sitting right up against the superconducting boundary.
Andrew Geraci, Northwestern: Is that we need to maintain a certain background magnetic field, so that the alarm or frequency the procession frequency of the helium.
Andrew Geraci, Northwestern: coincides with the target frequency that i'm spinning my my mass, and so I need to be able to set the background magnetic field at the sample.
Andrew Geraci, Northwestern: So this again is a little bit of a challenge with the superconducting wall next to the sample I can't just put a helmholtz coil around the whole system.
Andrew Geraci, Northwestern: So what I do is sort of a half homos coil or we call a D shaped coil so we use the fact that, if I have a D shaped current configuration next to the super new boundary.
Andrew Geraci, Northwestern: Then by the method of images, there will be a corresponding image current, on the other side of the boundary where the.
Andrew Geraci, Northwestern: The the current essentially along the wall goes in opposite directions and cancels out, and so this.
Andrew Geraci, Northwestern: Effectively, creates a situation where it looks like a helmets coil from the standpoint of where the where the object is located, and so this allows me then to keep a pretty nice uniform field at the at the sample which I can use to tune to set the set the background.
Andrew Geraci, Northwestern: So we're in the process of now finalizing the construction method for our soil sample blocks, so it has basically a system where we.
Andrew Geraci, Northwestern: attach together several pieces of courts that are patterned with electrodes and so forth, where we have this fear Royal area.
Andrew Geraci, Northwestern: Here, with these D shaped coils took to create the magnetic field bias field and then these gradient compensation coils and test excitation coil that we also have in the system to test the system by applying.
Andrew Geraci, Northwestern: known unknown rf field, so this is a image here, showing one of our earlier tests of fabricating one of these spiritual pockets, so the idea is that you take a piece of quartz.
Andrew Geraci, Northwestern: And you add a pit out of it, it has this sphere Royal shape and then you can take two of those and basically sandwich them together.
Andrew Geraci, Northwestern: and Polish down one of the faces to create this sphere oil cavity inside inside the piece of quartz, and so this is some of the initial.
Andrew Geraci, Northwestern: methods that we're using to create the cavity here within you can Polish down this material to eliminate some of the core irrigation so we've we're working with vendors to refine this process and we're now testing a latest batch that we just received last month.
Andrew Geraci, Northwestern: So, as I was mentioning also one of the key things in this experiment is to block regular magnetic noise and so.
Andrew Geraci, Northwestern: So the idea here is that this block will get coated with a thin film of Nairobi to screen ordinary genetic backgrounds and so we've been developing.
Andrew Geraci, Northwestern: methods, along with our partners in Korea to deposit sputtered Nairobi and then films.
Andrew Geraci, Northwestern: And so doing some test geometries, for example, to measure shielding factors and, for example, in this case on on on tubes and so we've been testing the.
Andrew Geraci, Northwestern: TC and so forth, and trying to improve the quality of the depositions for the for the sputtering we have some initial testing now that looks pretty promising on then film shielding where we have Nairobi.
Andrew Geraci, Northwestern: That has about 750 nanometers thickness so far, using this geometry, we have a theoretical shielding factor about 10 to eight we're measuring about 10 to the six so far.
Andrew Geraci, Northwestern: But we're we're confident that this can be still optimized by improving the purity of the of the Nairobi and.
Andrew Geraci, Northwestern: As and as another another method we've also been investigating we can actually use a separate very thin.
Andrew Geraci, Northwestern: foil in addition to that, then Nairobi and then, when we do this, then we demonstrate that we.
Andrew Geraci, Northwestern: got the feeling factor you actually expected from the geometry up to at the tender age level so so this looks very promising so tended to eight is sort of the benchmark we're trying to hit to get the.
Andrew Geraci, Northwestern: Full sensitivity of the experiment even 10 to the six you know, maybe good enough for the first round, but, but at least it looks promising for the ultimate sensitivity that that tend to the eight maybe maybe actually achievable with these 10 films.
Andrew Geraci, Northwestern: Of course that chilling factor is also driven by the level of magnetic background and one.
Andrew Geraci, Northwestern: One source of background, we have to be particularly worried about is impurities in the in the source mass itself, because if there was some such an impurity.
Andrew Geraci, Northwestern: And then, as we spend the source mass We might also modulate the magnetic field in a way that could potentially mask itself as the as a as an axiom.
Andrew Geraci, Northwestern: And so we did a fair amount of work characterizing the tungsten prototype source mass that we've been.
Andrew Geraci, Northwestern: Working on here now, in collaboration with our new partners at ptb so there they have a magnetic shielded room where they did some measurements in a squid.
Andrew Geraci, Northwestern: detector as well as using optical magnetometers so for initial measurements in the in the squid system they basically a magnetized the tungsten rotor and then D ghosted.
Andrew Geraci, Northwestern: To look at sort of residual magnetic fields that are present near the surface.
Andrew Geraci, Northwestern: The good news is that, after denouncing the field near the surface was seemed to be at around the Pico tessa level which is consistent with what you'd expect from Johnson noise, and this is.
Andrew Geraci, Northwestern: Roughly This is also consistent with the design sensitivity with with our shielding factor target have tended to eight to get eventually down to the ultimate sensitivity.
Andrew Geraci, Northwestern: So more sophisticated magnetic impurity mapping is something we've also recently done where we use higher resolution.
Andrew Geraci, Northwestern: optical magnetometers in the same shielded room environment over there, and this case, we can actually map out.
Andrew Geraci, Northwestern: The the magnetic environment near the wheel, and in this case, what we saw in the residuals was consistent with a few discrete.
Andrew Geraci, Northwestern: Isolated impurities near the surface of the rotor which could potentially been left for machining or some other other processes.
Andrew Geraci, Northwestern: But the but at least this way we can sort of understand the expected actual magnetic background from the thing but and the good news is that it seems to be small enough that we don't think this is going to be one of the limiting things in the in the experiment.
Andrew Geraci, Northwestern: we've also been characterizing the mechanism that that's that's going to rotate the tungsten rotor in the real experiment in particular our stage.
Andrew Geraci, Northwestern: So we've shown that the speed of the stage can be kept constant enough to utilize such a high.
Andrew Geraci, Northwestern: Quality factor, are key to basically we need to keep the device on resonance while we're driving it with the accion.
Andrew Geraci, Northwestern: And so the testing of that looks promising for achieving the required stability in the rotation speed we're also concerned about the any sort of wobble that occurs, while the.
Andrew Geraci, Northwestern: device is spinning, since this is going to basically set the minimum separation distance we can comfortably run the experiment.
Andrew Geraci, Northwestern: And so we we've been working on achieving a very stable system with surette precision ceramic bearings and ultra straight rod materials so here's an example of of the shaft that we attach the motor to the to the.
Andrew Geraci, Northwestern: tungsten wheel with this is a.
Andrew Geraci, Northwestern: rod that we've been testing with a brass prototype wheel where it's made of a titanium aluminum magnesium alloy.
Andrew Geraci, Northwestern: And we have a straightness that we've measured here that's better to better than about a half a thousandth of an inch.
Andrew Geraci, Northwestern: Which is within our tolerance to keep our separation distances here at the 50 micron level to get to the closest possible distances for the heaviest axons in the search.
Andrew Geraci, Northwestern: So in situ, we can keep an eye on the wobble of this device using fiber couple days are in her for amateurs which are.
Andrew Geraci, Northwestern: included will be included in the Christ at so here by monitoring the reflection of a laser from the bottom surface of the of the rotating wheel.
Andrew Geraci, Northwestern: and looking at its interference with light that comes from back from the tip of a fiber optic you can essentially create a very low finesse interferometer.
Andrew Geraci, Northwestern: which gives you a pretty good sensitivity to ascertain the the wobble of the experiment in situ, and so this is something that's still we're still in the process of studying and characterizing.
Andrew Geraci, Northwestern: The squid magnetometers that are using the experiment will be using experiment will be these here that are fabricated from our collaborators.
Andrew Geraci, Northwestern: in Korea and we're also looking at low noise gradiometer designs to potentially also help eliminate backgrounds from on one of the vibrations and so forth.
Andrew Geraci, Northwestern: So that's sort of the current state, so the we're hoping to we have the the main experimental Christ, that is, on order now from a vendor we're expecting to receive it towards the end of February.
Andrew Geraci, Northwestern: And we're excited to build the real system up now that we've tested some of these various key components of it.
Andrew Geraci, Northwestern: So I wanted to sort of end with a little bit of kind of future projection which I think makes me particularly excited.
Andrew Geraci, Northwestern: here about this this experiment and the other ones that we're hearing about this meeting.
Andrew Geraci, Northwestern: And I think that that what what's kind of interesting now, if you think about the all of the work going on in the field with existing unplanned experiments when we combine them together It really seems possible that.
Andrew Geraci, Northwestern: You know, perhaps not so distant future, will really be able to cover the entire QC de accion frequency band with sensitivity sufficient enough to to measure the expected accion couplings.
Andrew Geraci, Northwestern: And so, this is a plot I adapted from from Ken irwin also showing that, by using quantum techniques, one can potentially get even further, all the way down to the full sensitivity band over this huge mass range.
Andrew Geraci, Northwestern: So just to wrap up so Ariadne is a is an accion experiment that looks for the accion independent of dark matter of just using fifth for search based on Mr and where.
Andrew Geraci, Northwestern: The range of the experiment kind of sets the mass of the axon you search for so we're we're building our first generation to sort of address a current gap in current searches at the kind of hundred micro ev to a few mil ev range.
Andrew Geraci, Northwestern: It has a feature, I guess, this was something that Andrew in the previous talk also pointed out, where you don't have to scan any mass because you're basically looking at all the masses within our range simultaneously.
Andrew Geraci, Northwestern: This is certainly a nice aspect of it, and also the fact that it's not depending on any assumption about dark matter density.
Andrew Geraci, Northwestern: So, as I mentioned we're receiving the cryostat in February we're hoping to complete the construction on it by the end of the summer.
Andrew Geraci, Northwestern: And perhaps in the future, combined with the other efforts in our Community, will be able to really cover the entire allowed QC dx and window and with that I just want to acknowledge the folks in our group that are doing some other work and thanks everyone for your attention.
Christian Boutan: Thank you, Andrew that's a really nice talk um forgive me for mispronouncing Ariadne I see letters out of order um.
Andrew Geraci, Northwestern: No, no.
Christian Boutan: i'm questions for Andrew.
Christian Boutan: Chelsea.
Chelsea Lynn Bartram: yeah I have one i'm Chris thanks for the talk it was nice i'm just in general, so you know it sounds like it's fairly broadband if you discover a signal in this way.
Chelsea Lynn Bartram: What would kind of be your first steps to you investigate that and determine that it wasn't some like you mentioned due to some impurities or some other factor.
Andrew Geraci, Northwestern: yeah I know it's a it's a great question right so.
Andrew Geraci, Northwestern: So the nice thing about this experiment, I think, is that we're sort of controlling the source of the signal right, so you have the opportunity to, for example, swap out the material of the of the of the rotor.
Andrew Geraci, Northwestern: For example, but will also you know one thing that I think is going to be nice to distinguish real sort of accion signals from backgrounds, is the fact that we have.
Andrew Geraci, Northwestern: Multiple sensors around the the spinning device, and so we know the phase of the rotation of the source, and so we know basically how the phase of the processing spin.
Andrew Geraci, Northwestern: In adjacent sensors should should be relative to each other, and so, so this may be another way, we can sort of tease out, you know.
Andrew Geraci, Northwestern: background noise or whatever at these at these signals in the most dangerous backgrounds, for us, are ones where there's.
Andrew Geraci, Northwestern: occurring at the same period as as the accion so one example of that would be like from the barnett effect which I didn't really explain much about, but if I have this.
Andrew Geraci, Northwestern: magnification that sort of uniform mechanization of the rotor that occurs just from its rotation it's a really tiny effect.
Andrew Geraci, Northwestern: But if my magnetic shield was not good enough, then i'm in principle would be able to see that and that's actually one thing we're trying to.
Andrew Geraci, Northwestern: Think about using as a calibration tool for the experiment, but so so but, but that we need to have the magnetic shield operating well enough to screen, that in order for that not to be to be a problem.
Christian Boutan: With your questions from do you have any synergy with tours and balance experiments, is it is there anything that you're developing that would be useful to them or or vice versa.
Andrew Geraci, Northwestern: yeah that's interesting I mean, I think you know a lot of the stuff we're doing with.
Andrew Geraci, Northwestern: operating a very low magnetic field background getting rid of magnetic noise could potentially be relevant so, for example, if.
Andrew Geraci, Northwestern: If some of these other precision tours and bounds experiments are sensitive to magnetic backgrounds impurities.
Andrew Geraci, Northwestern: or need magnetic shielding I mean this this aspect, I think, maybe could be.
Andrew Geraci, Northwestern: You know in common it's so it's it's it's sort of in the same spirit as a lot of these towards males burn incense that you're looking for this kind of force in many cases they have.
Andrew Geraci, Northwestern: A wide array of torsion balance, you know spin dependent force experiments, except we're just now using the mmr is the sensor instead of the tours and mouse, so you can imagine, there are some considerations, depending on the particular experiment.
cool.
Christian Boutan: And and you're looking for a different coupling but um but you're sort of in the sort of mad Max range a little bit so if there was a signal, one of the you know you could confirm it or they can confirm it.
Andrew Geraci, Northwestern: yeah I think that's right, so I mean so as I, as I mentioned that the range for us is sort of set by the you know the constant wavelength, of the axon, and so I could build the experiment, for example, to focus more on.
Andrew Geraci, Northwestern: On a few mil ED or we could build an experiment that would be very sensitive at at a few micro TV so.
Andrew Geraci, Northwestern: I think if there was a detection and from others from some other experiment, we would we would tailor and experiment try to measure the accent coupling to nucleotides.
Andrew Geraci, Northwestern: If, for example, it was detected, first through the coupling the photons so so there's actually quite a bit of tune ability we chose to build the first round of the experiment.
Andrew Geraci, Northwestern: To particularly address a gap where no one's really looking right now, where it seemed like it's going to be quite a while before anyone's going to have a different technique to measure.
Andrew Geraci, Northwestern: At the masses that we're we're aiming at, and so we, we can go a bit higher, I think, then, what mad Max has been able to.
Andrew Geraci, Northwestern: To to sort of project anyway.
Great.
Christian Boutan: Other questions for Andrew.
Christian Boutan: Okay, great well with that, thank you very much, Andrew um.
Christian Boutan: That was a great talk.
let's move on to a cash.
Christian Boutan: When you hear about.
Christian Boutan: photon counting.
Christian Boutan: Radio crashing.