Events at Physics

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Events During the Week of September 3rd through September 10th, 2023

Monday, September 4th, 2023

Academic Calendar
Labor day
Abstract: *Note: actual end time may vary.* URL:
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Tuesday, September 5th, 2023

Cookie Potluck
Time: 2:00 pm - 3:00 pm
Place: Univ Ave foyer (outside 2241 CH)
Abstract: We invite the bakers out there to bring a batch of your best to share! If you’re not a baker or don’t have time, just come hang out with us for a bit to have a cookie. For the bakers, it’d be helpful if you can mark anything that has nuts (we’ll assume most baked goods have butter, eggs and flour).
Host: PGSC (Jarret Rosenberg/Zachary Jerzyk) + UW-Physics (Sharon Kahn)
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Hunting the origin of ultrahigh-energy cosmic rays through neutrinos and gamma-rays
Time: 2:30 pm - 3:30 pm
Place: WIPAC supernova /
Speaker: Saikat Das, Yukawa Institute, Kyoto University, Japan
Abstract: Ultrahigh-energy cosmic rays (UHECRs) are the highest-energy particles observed in the Universe, with their energy spectrum extending beyond a few times 1e20 eV. Their unknown sources can also contribute to the diffuse astrophysical neutrino flux measured by IceCube in the TeV-PeV energy range. By modelling their multi-wavelength energy spectrum, we probe cosmic ray acceleration in high-energy gamma-ray sources such as active galactic nuclei and gamma-ray bursts. In particular, I will discuss models explaining the correlation of a high-energy neutrino event from the direction of the Fermi-LAT gamma-ray blazar TXS 0506+056, and the >10 TeV afterglow emission in GRB 221009A. Using a luminosity-dependent density evolution, I will also present the PeV-EeV diffuse neutrino flux from the entire blazar population. For a generic source distribution, the detection of cosmogenic neutrinos beyond ~0.1 EeV is favourable by upcoming detectors, such as IceCube Gen-2, GRAND and POEMMA, depending on the UHECR mass composition. Lastly, I shall discuss the superheavy dark matter origin of the high-energy cosmic rays, gamma rays, and neutrinos.
Host: Ke Fang
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Academic Calendar
Graduate School Fall 2023: Fall degree window period deadline for master&#39;s students
Time: 4:00 pm - 5:00 pm
Abstract: CONTACT: 262-2433,
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Academic Calendar
Graduate School Fall 2023: Fall degree window period deadline for doctoral students
Time: 11:55 pm - 12:55 am
Abstract: Degree candidates must complete all steps: *Important Note: The “Window Period” is the time between the end of one degree period and the beginning of the next. You must have been registered for the previous semester (Fall, Spring, or Summer). If all degree requirements are met by the end of the window period, your degree will be granted for the following semester. However, you will not have to register or pay fees for the next semester. CONTACT: 262-2433,
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Wednesday, September 6th, 2023

Academic Calendar
Fall semester instruction begins
Abstract: *Note: actual end time may vary.* URL:
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Thursday, September 7th, 2023

No events scheduled

Friday, September 8th, 2023

Graduate Program Event
Advances in All-Optical Magnetometry for Femto-Tesla Sensitivity in Earth-Field-Scale Magnetic Fields
Time: 9:00 am - 10:30 am
Place: 5280 Chamberlin
Speaker: Michael Bulatowicz, Department of Physics Graduate Student
Abstract: The ability to detect femto-Tesla ($10^{-15}$) magnetic fluctuations in the presence of large background magnetic fields encountered in unshielded environments on Earth is a capability which can enable a wide array of applications presently requiring magnetically shielded environments. This has been possible for many years through the use of superconducting quantum interference devices (SQUIDs); however, SQUIDs are expensive to purchase, operate, and maintain. In contrast to SQUIDS, optically pumped magnetometers based on warm alkali vapor are relatively inexpensive to purchase, operate, and maintain while promising similar sensitivity capabilities.

In the present work, I have demonstrated an optically pumped scalar magnetometer using a 1 cm diameter by 1 cm length internal dimension cylindrical vapor cell with a photon shot noise limit of 3.5 $fT/\sqrt{Hz}$ and a demonstrated single-channel noise of 10 $fT/\sqrt{Hz}$ as limited by the electrical current source generating a 29 $\mu T$ bias field. I have further demonstrated a differential pair of these magnetometers, separated by a distance of 9 cm, with measured differential noise of 1 $fT cm^{-1}/\sqrt{Hz}$, consistent with a single-channel noise of 6 $fT/\sqrt{Hz}$. I present a straightforward procedure for optimization of the sensitivity of this magnetometer to achieve fundamental sensitivity limits in the low single digit $fT/\sqrt{Hz}$ and guidelines for detection electronics supporting total noise from the magnetometer dominated by the fundamental sensitivity limit. I demonstrate, analyze, and characterise the basis of a method for detection of the vector components of the incident magnetic field through the use of an applied oscillating field along each vector axis to be measured, and I present initial results with single-axis vector component detection. Included in the relevant chapter are algorithms and feedback methods for achieving high performance, along with a demonstration of each, and measurements of performance including relative accuracy and uncertainty. I further present a demonstration and theory of detection of RF magnetic fields near the natural Larmor precession frequency of the spins, taking advantage of the AC Stark shift of the optical pump beam to generate a linear sensitivity to the RF signal, measured at the difference between the RF frequency and Larmor frequency. Finally, I look toward future work, proposing a method for measurement of the vector direction of the incident magnetic field by real-time observation of the spin precession.
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Physics Department Colloquium
Time: 3:30 pm - 5:00 pm
Abstract: You should plan to attend the Department Picnic, tomorrow, Saturday, September 9!
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Saturday, September 9th, 2023

UW Madison Physics Department Picnic
Time: 11:00 am - 1:00 pm
Place: Garner Park, 333 S. Rosa Road
Abstract: All Physics Picnic! All are welcome - we hope you'll bring spouse, partners, kids! Garner Park has a playground, basketball courts, tennis courts, a big open field for soccer or frisbee. And a shelter - so the picnic will happen, rain or shine! Easy to get to by bike (~4.6 mi from Chamberlin) or by bus (Route A leaves University @ N. Orchard). RSVP:
Host: Sharon Kahn
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