Materials for Bright Beams Workshop 2025

Contribution List

35. Welcome

J. Ritchie Patterson

7/16/25, 8:45 AM

1. Workshop charge

Lance Cooley (Applied Superconductivity Center, NHMFL, Florida State University)

7/16/25, 8:50 AM

8. Photocathode Opening Talks (Convenor: Jamie Rosenzweig)

7/16/25, 9:05 AM

9. Superconducting RF Cavities Opening Talks (Convenor: Steve Sibener)

7/16/25, 10:45 AM

34. Perspectives from DOE OHEP

Derun Li (DOE OHEP)

7/16/25, 12:00 PM

11. High Gradient Opening Talks (Convenor: John Power)

7/16/25, 1:30 PM

29. Photocathodes Session 1 (Convenor: Sami Tantawi)

7/16/25, 3:15 PM

24. Superconducting RF Cavitiy Session 1 (Convenor: Alex Gurevich)

7/17/25, 8:00 AM

28. High-Gradient Structures Session 1 (Convenor: Evgenya Simakov)

7/17/25, 10:15 AM

12. Photocathode Session 2 (Convenor: Lance Cooley)

7/17/25, 1:15 PM

13. Superconducting RF Cavity 2 (Convenor: Anne-Marie Valente-Feliciano)

7/17/25, 3:30 PM

32. Industry Blitz (Convenor: John Power)

7/17/25, 5:15 PM

14. Dinner and Poster Session - Baker Portico (Postdoc and Grad Student Poster Session)

7/17/25, 6:05 PM

27. High-Gradient Structures 2 (Convenor: Danny Perez)

7/18/25, 8:30 AM

16. Summary Talks

7/18/25, 10:40 AM

18. Facility Tours

7/18/25, 12:45 PM

2. Accelerator Materials Session

3. Accelerator Materials Talk

4. Accelerator Materials Talk

5. Accelerator Materials Talk

6. Accelerator Materials Talk

7. Accelerator Materials Talk

19. CBETA Tour

52. Co-sputtering of Nb3Sn into SRF cavity using composite target and optimizing surface homogeneity

Md Sharifuzzaman Shakel (OLD DOMINION UNIVERSITY)

Nb₃Sn is a promising alternative to bulk Nb for superconducting radiofrequency (SRF) cavities due to its higher critical temperature (Tc ~18.3 K) and superheating field (Hsh ~400 mT), enabling improved cryogenic efficiency. Nb₃Sn coating method for superconducting radiofrequency (SRF) cavity has been developed following co-sputtering of Nb-Sn composite target using a DC cylindrical sputter...

53. Correlating Atomic-Scale Structure with Superconducting Properties for Metallic, (3x1)-Oxidized, and Nitrogen-Dosed Nb(100)

Mr Michael Van Duinen (University of Chicago)

Superconducting radio frequency (SRF) cavities are the fundamental accelerating components of linear particle accelerators. Niobium is the material of choice for SRF cavities due to its high malleability, thermal conductivity, and superconducting critical temperature (T_C). Despite Nb having a T_C of ~9 K, the practical operating temperature of a Nb SRF cavity is ~2 K, below the boiling point...

38. Development of a Plasma-Enhanced Chemical Vapor Deposition System for High-Performance SRF Cavities and Thin Film Studies

Gabriel Gaitan

Next-generation, thin-film surfaces employing Nb3Sn, NbN, NbTiN, or other compound superconductors are essential for reaching enhanced RF performance levels in SRF cavities. However, optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University developed and commissioned a...

45. Development of a Plasma-Enhanced Chemical Vapor Deposition System for High-Performance SRF Cavities and Thin Film Studies

Gabriel Gaitan

Next-generation, thin-film surfaces employing Nb3Sn, NbN, NbTiN, or other compound superconductors are essential for reaching enhanced RF performance levels in SRF cavities. However, optimized, advanced deposition processes are required to enable high-quality films of such materials on large and complex-shaped cavities. For this purpose, Cornell University developed and commissioned a...

55. Development of Sodium Potassium Antimonide Photocathodes for Electron Cooling at Brookhaven National Laboratory

Kali Mondal (Brookhaven National Laboratory)

The success of electron cooling [1,2] for the Electron-Ion Collider (EIC) relies on the development of high-performance photocathodes (PCs) for photoinjectors. Ideal PCs are expected to exhibit high quantum efficiency (QE), low emittance, long operational lifetime, and minimal dark current. Alkali antimonide photocathodes are strong candidates to meet these demanding requirements. Among them,...

22. Electron Microscopes Tour

20. Hercules and Medusa Tour

37. High power RF testing of high-temperature superconductors

Ankur Dhar (SLAC National Accelerator Lab)

Superconducting materials such as niobium have been extremely useful for accelerator technology but require low temperature operation ~2 K. The development of high temperature superconductors (HTS) is promising due to their operating temperatures being closer to that of liquid nitrogen ~77 K. This work aims to determine the high-power RF performance of these materials at X-band (11.424 GHz)....

43. Identifying the connections between grain growth and flux expulsion in low RRR niobium SRF cavities

Katrina Howard (University of Chicago)

The SRF community has shown that high temperature annealing can improve the flux expulsion of niobium cavities during cooldown. The required temperature will vary between cavities and different batches of material, typically around 800 C and up to 1000 C. However, for niobium with a low residual resistance ratio (RRR), even 1000 C is not enough to improve its poor flux expulsion. The purpose...

47. Improving 1-D TD-DFT Simulations of Optical Field Emission from Nanopatterned Cathodes

Joshua Mann

Nanopatterned cathodes, operating under the strong optical field emission regime, are promising candidates for high brightness electron beam generation. Previous theoretical studies have indicated that brightness monotonically increases with the enhanced laser intensity, provoking the thermomechanical studies to determine the cathodes’ limits. We present an in-progress ab initio calculation of...

31. Industry Blitz

49. Inelastic electron scattering in photoemission

W. Andreas Schroeder (University of Illinois Chicago)

The emission of photo-excited electrons through inelastic scattering mechanisms is demonstrated to be prevalent in both semiconductor and metal photocathodes. This type of Franck-Condon process requires an intermediate ‘particle’ to simultaneously satisfy momentum and energy resonant electron emission into the vacuum states; optical phonons in polar semiconductors and the reciprocal lattice...

44. Investigating Dirac semimetal cadmium arsenide as a potential low-MTE photocathode

Truman Idso (Arizona State University)

We report on the quantum efficiency (QE) and mean transverse energy (MTE) of photoemitted electrons from cadmium arsenide $(\mathrm{Cd_3As_2})$, a three-dimensional Dirac semimetal (3D DSM) of interest for photocathode applications due to its unique electronic band structure, characterized by a 3D linear dispersion relation at the Fermi energy. Samples were synthesized at the National...

21. Low Emittance Beamline Tour

40. Measurements of Stability Diagrams in the IOTA Ring at Fermilab

MaryKate Bossard

Nonlinear focusing elements enhance the stability of particle beams in high-energy colliders via Landau Damping, a phenomenon that acts through the tune spread these elements introduce. This experiment at Fermilab's Integrable Optics Test Accelerator (IOTA) aims to investigate the influence of nonlinear focusing elements on transverse beam stability by employing a novel method to directly...

39. Molecular beam epitaxial growth of sodium antimonide photocathodes

Elena Echeverria

The Center for Bright Beams (CBB) at Cornell University has been developing techniques to grow single-crystal photocathodes for electron sources using molecular beam epitaxy (MBE). As a result, the first single-crystal Cs3Sb photocathode was produced, which has shown high quantum efficiency and is expected to have a low mean transverse energy (MTE). Now, other alkali materials are being...

46. MTE and QE Behavior of Cs₃Sb Photocathodes under Varying Wavelengths at Room and Cryogenic Temperatures

Peter Owusu (Arizona State University)

The ASU cryogenically cooled DC electron gun offers an advanced platform for photocathode testing at room and cryogenic temperatures. Using a four-dimensional phase space reconstruction via the pinhole scan technique, we measure the Mean Transverse Energy (MTE) of alkali antimonide photocathodes, providing comprehensive experimental validation of the theory predicting reduced (MTE) near the...

51. Oxidation Studies of Au Capped Nb Surfaces

Van Do

Niobium surfaces readily form thick, non-superconducting oxide layers that can severely degrade radio frequency performance. These oxides create surface hot spots, which can lead to vortex nucleation and ultimately cause cavity quenching. We aim to prevent this deleterious Nb oxide formation by capping Nb surfaces with thin gold layers. We deposited gold layers ranging from ultra-thin (0.25...

17. Photocathodes Session

30. Photocathodes Session

50. Picometer-scale emittance and space charge effects in nanostructured photocathodes

Anagha Ullattuparambil (Arizona State University)

Generation of ultralow-emittance electron beams with high brightness is critical for several applications such as ultrafast electron diffraction, microscopy, and advanced accelerator techniques. By leveraging the differences in work function and electronic structure between different materials, we enabled spatially localized photoemission, resulting in picometer-scale emittance from a flat...

57. Progress on New Compound Superconductors for SRF Cavities

Nathan Sitaraman

Nb3Sn has led the way among higher-Tc alternatives to Nb for SRF applications, but it is still very far from its fundamental limits, especially in terms of quench field. While it is tempting to consider superconductors with even higher fundamental limits, we take an alternative approach, learning from the challenges encountered in Nb3Sn R&D and exploring materials that could more easily...

23. SRF Facility Tour

25. SRF Tour

42. Status of the CYBORG beamline at UCLA: First Room Temperature Photoelectrons, soon available at 80 K!

Fabio Bosco

The intrinsic emittance obtained from radio-frequency (RF) photoinjectors is notably reduced by increasing the launch field at the cathode. Moreover, cryogenic RF guns offer the possibility of producing stronger fields, due to the higher bulk conductivity and lower breakdown rate, while reducing the mean transverse energy (MTE) of near-threshold photo electrons. Such devices thus constitute an...

56. Studies of Nb in Preparation for Gold Capping Layers

Sadie Seddon-Stettler

Bulk niobium is the standard material of choice for superconducting radio frequency (SRF) cavities for accelerator applications. However, the native niobium oxide that forms when niobium is exposed to atmosphere may inhibit cavity performance. Ongoing work at Cornell University proposes to chemically remove the niobium oxide and replace it before it can reform with a sub-nm layer of...

26. Summary Talks 30 minutes each, at least

41. Synthesis of ordered Na-K-Sb photocathodes with oxygen-enhanced quantum efficiency

Abigail Flint

Alkali antimonide photocathodes are recognized for their efficacy as photoemissive materials in electron sources. This study investigates the fabrication of ordered films of sodium potassium antimonide via Molecular-Beam Epitaxy (MBE) and the impact of oxygen on their performance at the PHOtocathode Epitaxy Beam Experiments (PHOEBE) laboratory within the Center for Bright Beams (CBB) at...

48. Tuning Niobium Oxides for Sn Nucleation

Jasper Brown, Liana Shpani, Van Do

With a critical temperature twice that of niobium, Nb$_3$Sn is the most promising alternative material for the future of Superconducting Radio-Frequency (SRF) technology, steadily advancing towards practical applications. In this collaborative study, we developed a framework to synthesize, characterize and compare substrate preparations based on oxide composition and surface roughness, aiming...

33. Workshop Summary

54. Zr-Nb Surface Alloys for Thermally Stable, Low-Loss SRF Cavities

Robert Burnley

Superconducting radiofrequency (SRF) cavities are limited by losses that originate in the top ~100 nm of the niobium surface. Zr–Nb alloys offer a promising route to reducing these losses by passivating the surface with ZrO2 and suppressing lossy Nb2O5. In this project, we alloy Zr into Nb through evaporation and thermal diffusion, building on methods developed for Nb3Sn films. Our goal is to...