Scientist Interview: David Joffe

In this interview, Dr. David Joffe (Associate Professor of Physics at Kennesaw State University, Georgia) discusses an exciting new program he is directing as faculty advisor for his university’s Society of Physics Students to encourage undergraduate physics students to take an active role in the future of muography by building muography detectors.

Inspired by the Scan Pyramids Project and the 3rd generation muography detectors (developed at Wigner RCP, Hungary and UTokyo, Japan) new prototypes for wire-chamber detectors are being built and designed by the next generation of muographers.  As the muon detector prototypes near completion, he also discusses plans to investigate archeological sites, such as pre-contact Mississippian Culture mounds.  There are several of these sites in the Midwestern, Eastern, and Southeastern United States and he hopes that this program will impel other universities to start similar programs to generate real world experience for physics students and expand the potential of muography.

Q:  When did you first learn about the muography technique and what aspects of the technique most interest you?

I first learned about muography when I was a postdoc working on the commissioning of the ATLAS detector at CERN. The tracking groups were looking at cosmic rays in the detector before the first collisions and I remember people talking about how a similar thing could be done with cosmic ray muons in archaeological structures. I was in the calorimetry group looking at photon conversions in the tracker and using GEANT to simulate how to use the conversion vertices to make a 3-D density map of the calorimeter, so I was interested in what the tracking people were doing and curious about how those techniques could be used for density mapping and imaging.

Q:  Please discuss your work with the Society of Physics Students at Kennesaw State University, Georgia.   What has been the progress with your program to build muography detectors?  Have you done any tests of the detectors yet?

We’ve been building a series of prototypes over the last year using different materials, different types of wire, etc. We based our first prototypes on papers we found by the group in Budapest (Olah, Varga, et al.) and adapted their design somewhat based on what we could construct in our undergraduate lab space. Learning how to use the equipment we had to build chambers that could hold high voltage without any current leak and also without leaking the Ar/CO2 as well which was a big step forward for us.  Now we’re working with beta sources trying to figure out the best way to deal with pulses and output electronics to get the cleanest signal we can.

Q:  One of the potential targets for muography imaging with your new program are “pre-contact Mississippian Culture mounds”, many of which are located in your local area.  Where do these ruins originate from, why are they ideal targets for muography and how is muography uniquely suited to imagining these structures?

The mounds were built by the ancestors of today’s native Americans in the central and southern United States; they vary somewhat in age but most of the largest ones are between 800-1000 years old. Part of what makes the mounds good targets for muography is that they are fairly large (up to 30 m high) and have a relatively simple geometry on the outside. But one of the most exciting things is the sheer number of them, there are 60-70 mound complexes scattered around the country with hundreds of individual mounds to investigate, most of which have never been excavated. There are a large number of universities in the US that have these types of sites within a short driving distance from the campus; for us the nearest site is only a 20 minute drive away.

Q:  Besides the mounds, are there other imaging targets or collaborations that you are considering once you have built a reliable, robust muon detector prototype?

Our hope is that we could get other universities in the US to join us and investigate the mounds in their areas. It’s been a great experience for the Society of Physics Students at Kennesaw State to work on building and designing their own wire chambers, it’s definitely something other SPS chapters or undergraduate research groups could think about doing.

Q:  When did this program to build muography detectors start?  How many students are involved and how have they benefitted from the experience?

The project itself started in the fall of 2017 when a group of undergraduate students from the Student Physics Society  approached me with the idea that they wanted to start their own project that could really be “theirs”. I suggested the wire-chamber/muography project knowing that there were multiple mound sites nearby to investigate once they had chambers working. But I have (as much as possible) attempted to let the undergraduates work out the details for themselves; this project is really as much about giving the best hands-on learning experience to the students as it is about the wire chambers.

That’s the part that’s been really exciting; so far five of the students have presented at national conferences, with two winning top presentation awards at the APS April meeting and three of the students having written proceedings which will soon be published. Two of the students won awards from a local company (Birla Carbon) to work full time in the summer building the prototypes, and one of them has now been accepted to Vanderbilt this fall on a University Fellowship to do doctoral work on the PHENIX experiment.

The students have had a really great reception from the general physics community; even though our chambers are relatively simple by the standards of the big experiments I think people are impressed that this is something that undergraduates are learning to do by themselves. And it’s starting to pay off for them in terms of graduate school acceptences, publications, awards, internships etc. So to me the project is as much about the potential of working with undergraduates (at Kennesaw State we are an undergraduate-focused department) as it is about the wire chambers themselves. For me that’s probably the most exciting part of the story, because I think people often underestimate what kind of research activity undergraduate students are capable of doing given the right opportunity.

Q:  Can you can tell me about the cross-disciplinary collaboration with the Electrical Engineering and how are they involved?

One of the students who was working with us is from the Electrical Engineering department. The Electrical Engineering department also let us use their Network Analyzer so that we could look at the frequency response of the chambers we built and we hope to continue working with them.

Q:  I read about educational programs that you conduct at Kennesaw State University with elementary and middle school students.  Has the Society of Physics Students been involved and have they highlighted your muography research?

KSU is an affiliate of the Georgia Space Grant Consortium program which is funded by NASA, and the SPS students have been active in the outreach portion of that program. They’ve given presentations about the wire chambers to groups of students at several local high schools and we’ve had a really good response. The outreach to local high schools is definitely something we plan to continue.

The undergraduate group of the muography detector program at the Kennesaw State University Society of Physics Students is (from left to right in the photo above) Jake Whelchel, Emma Pearson, Allen Townsend and Michael Reynolds.

For more information about this program from the student’s perspective, check the following interview on the Kennesaw State University website:

“Passing the Torch: Physics Major Takes on the Cosmos”