NAPAC2022 - List of Keywords (cryogenics)

Paper	Title	Other Keywords	Page
MOPA24	LCLS-II and HE Cryomodule Microphonics at CMTF at Fermilab	cavity, cryomodule, SRF, niobium	103
	C. Contreras-Martinez, B.E. Chase, A.T. Cravatta, J.A. Einstein-Curtis, E.R. Harms, J.P. Holzbauer, J.N. Makara, S. Posen, R. Wang Fermilab, Batavia, Illinois, USA L.R. Doolittle LBNL, Berkeley, California, USA
	Microphonics causes the cavity to detune. This study discusses the microphonics of 16 cryomodules, 14 for LCLS-II and 2 for LCLS-II HE tested at CMTF. The peak detuning, as well as the RMS detuning for each cryomodule, will be discussed. For each cryomodule, the data was taken with enough soaking time to prevent any thermalization effects which can show up in the detuning. Each data capture taken was 30 minutes or longer and sampled at 1 kHz.
	Poster MOPA24 [1.428 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA24
About •	Received ※ 03 August 2022 — Revised ※ 10 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 20 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA46	Cryogenic Dielectric Structure with GΩ/m Level Shunt Impedance	impedance, simulation, acceleration, accelerating-gradient	157
	R.A. Kostin, C. Jing Euclid Beamlabs, Bolingbrook, USA
	Shunt impedance is one of the most important parameters characterizing particle acceleration efficiency. It is known that RF losses are reduced at cryogenic temperatures. For example, a record high shunt impedance of 350 MΩ/m was demonstrated recently for all metal X-band accelerating structure, which is more than 2 times higher than that at room temperature. In this article we present a novel hybrid dielectric structure which can achieve even higher shunt impedance due to the fact that losses in dielectric materials reduced much more than in pure copper.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA46
About •	Received ※ 12 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 23 August 2022 — Issue date ※ 17 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUYD6	Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations	cathode, gun, electron, MMI	292
	G.S. Gevorkyan, T.J. Hanks, A.H. Kachwala, S.S. Karkare, C.J. Knill, C.A. Sarabia Cardenas Arizona State University, Tempe, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams, and the DOE under Grant No. DE-SC0021092. We present the first results of the commissioning of the 200 kV DC electron gun with a cryogenically cooled cathode at Arizona State University. The gun is specifically designed for studying a wide variety of novel cathode materials including single crystalline and epitaxially grown materials at 30 K temperatures to obtain the lowest possible intrinsic emittance of UED and XFEL applications [1]. We will present the measurements of the cryogenic performance of the gun and the first high voltage commissioning results. [1] G. S. Gevorkyan et. al., Proc. of NAPAC19 MOPLM16 (2019)
	Slides TUYD6 [12.632 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD6
About •	Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA80	Cyborg Beamline Development Updates	gun, cathode, cavity, simulation	512
	G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai UCLA, Los Angeles, California, USA F. Bosco Sapienza University of Rome, Rome, Italy Z. Li, S.G. Tantawi SLAC, Menlo Park, California, USA B. Spataro LNF-INFN, Frascati, Italy
	Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409. Xray free electron laser (XFEL) facilities in their current form are large, costly to maintain, and inaccessible due to their minimal supply and high demand. It is then advantageous to consider miniaturizing XFELs through a variety of means. We hope to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end we have designed and fabricated our new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). The photogun is 0.5 cell so much less complicated than our eventual 1.6 cell photoinjector. It will serve as a prototype and test bed for cathode studies in a new cryogenic and very high gradient regime. We present here the fabricated structure, progress towards commissioning, and beamline simulations.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA80
About •	Received ※ 02 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 09 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA81	Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure	cavity, GUI, distributed, electron	516
	G.E. Lawler, A. Fukasawa, J.R. Parsons, J.B. Rosenzweig UCLA, Los Angeles, California, USA Z. Li, S.G. Tantawi SLAC, Menlo Park, California, USA A. Mostacci Sapienza University of Rome, Rome, Italy E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA B. Spataro LNF-INFN, Frascati, Italy
	Funding: This work was supported by the DOE Contract DE-SC0020409. High-gradient RF structures capable of maintaining gradients in excess of 250 MV/m are critical in several concepts for future electron accelerators. Concepts such as the ultra-compact free electron laser (UC-XFEL) and the Cool Copper Collider (C3) plan to obtain these gradients through the cryogenic operation (<77K) of normal conducting copper cavities. Breakdown rates, the most significant gradient limitation, are significantly reduced at these low temperatures, but the precise physics is complex and involves many interacting effects. High-power RF breakdown measurements at cryogenic temperatures are needed at the less explored C-band frequency (5.712 GHz), which is of great interest for the aforementioned concepts. On behalf of a large collaboration of UCLA, SLAC, LANL, and INFN, the first C-band cryogenic breakdown measurements will be made using a LANL RF test infrastructure. The 2-cell geometry designed for testing will be modifications of the distributed coupled reentrant design used to efficiently power the cells while staying below the limiting values of peak surface electric and magnetic fields.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA81
About •	Received ※ 29 July 2022 — Accepted ※ 02 August 2022 — Issue date ※ 08 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEZE4	First High-Gradient Results of UED/UEM SRF Gun at Cryogenic Temperatures	gun, cavity, SRF, accelerating-gradient	607
	R.A. Kostin, C. Jing Euclid Beamlabs, Bolingbrook, USA D.J. Bice, T.N. Khabiboulline, S. Posen Fermilab, Batavia, Illinois, USA
	Funding: The project is funded by DOE SBIR #DE-SC0018621 Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, we present first high gradient results of the gun conducted in liquid helium.
	Slides WEZE4 [2.817 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZE4
About •	Received ※ 05 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA32	Spallation Neutron Source Cryogenic Moderator System Helium Gas Analysis System	MMI, neutron, operation, target	699
	B. DeGraff, L. Pinion ORNL RAD, Oak Ridge, Tennessee, USA R. Armstrong, J. Denison, M.P. Howell, S.-H. Kim, D. Montierth ORNL, Oak Ridge, Tennessee, USA M.D. Williamson LBNL, Berkeley, California, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) operates the Cryogenic Moderator System (CMS). The CMS comprises a 20-K helium refrigerator and three helium to hydrogen heat exchangers in support of hydrogen cooled spallation moderation vessels. This system uses vessels filled with activated carbon as the final major component to remove oil vapor from the compressed helium in the cryogenic cold box. SNS uses a LINDE multi-component gas analyzer to detect the presence of contaminants in the warm helium flow upstream of the cold box including aerosolized oil vapor. The design challenges of installing and operating this analyzer on the CMS system due to normal system operating pressures will be discussed. The design, fabrication, installation, commissioning, and initial results of this system operation will be presented. Future upgrades to the analyzer system will also be discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA32
About •	Received ※ 06 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 05 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA66	Near-Threshold Photoemission from Graphene Coated Cu Single Crystals	electron, cathode, experiment, brightness	776
	C.J. Knill, S.S. Karkare Arizona State University, Tempe, USA H. Ago, K. Kawahara Global Innovation Center, Kyushu University, Kasuga, Fukuoka, Japan E. Batista, N.A. Moody, G.X. Wang, H. Yamaguchi, P. Yang LANL, Los Alamos, New Mexico, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams, and by the Department of Energy under Grant DE-SC0021092. The brightness of electron beams emitted from photocathodes plays a key role in the performance of x-ray free electron lasers (XFELs) and ultrafast electron diffraction (UED) experiments. In order to achieve the maximum beam brightness, the electrons need to be emitted from photocathodes with the smallest possible mean transverse energy (MTE). Recent studies have looked at the effect that a graphene coating has on the quantum efficiency (QE) of the cathode [1]. However, there have not yet been any investigations into the effect that a graphene coating has on the MTE. Here we report on MTE and QE measurements of a graphene coated Cu(110) single crystal cathode at room and cryogenic temperatures. At room temperature, a minimum MTE of 25 meV was measured at 295 nm. This MTE remained stable at 25 meV over several days. At 77 K, the minimum MTE of 9 meV was measured at 290 nm. We perform density functional theory (DFT) calculations to look at the effects of a graphene coating on a Cu(111) surface state. These calculations show that the graphene coating reduces the radius of the surface state, allowing for emission from a lower transverse energy state in comparison to bare Cu(111). [1] F. Liu et al, Appl. Phys. Lett. 110, 041607 (2017); https://doi.org/10.1063/1.4974738
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA66
About •	Received ※ 28 July 2022 — Revised ※ 19 July 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYE4	Development of an Ultra-Low Vibration Cryostat Based on a Closed-Cycle Cryocooler	vacuum, radiation, instrumentation, synchrotron	874
	R.W. Roca Illinois Institute of Technology, Chicago, Illinois, USA E.W. Knight, R.A. Kostin, Y. Zhao Euclid TechLabs, Solon, Ohio, USA
	Low temperature and low vibration cryostats are useful in a variety of applications such as x-ray diffraction, quantum computing, x-ray monochromators and cryo-TEMs. In this project, we explore an ultra-low vibration cryostat with the cooling provided by a closed cycle cryocooler. Closed-cycle cryocoolers inevitably introduce vibrations into the system, and in this project, flexible copper braiding was used to decouple vibrations and provide cooling at the same time. In order to develop the cryostat, capacity map of a two stage Sumitomo cryocooler was measured as well as vibration transmission through different copper braids using an IR interferometer. This paper covers the capacity map and vibration measurements in the first prototype.
	Slides THYE4 [4.989 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYE4
About •	Received ※ 16 July 2022 — Revised ※ 10 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 12 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPA24

LCLS-II and HE Cryomodule Microphonics at CMTF at Fermilab

cavity, cryomodule, SRF, niobium

103

C. Contreras-Martinez, B.E. Chase, A.T. Cravatta, J.A. Einstein-Curtis, E.R. Harms, J.P. Holzbauer, J.N. Makara, S. Posen, R. Wang
Fermilab, Batavia, Illinois, USA
L.R. Doolittle
LBNL, Berkeley, California, USA

Microphonics causes the cavity to detune. This study discusses the microphonics of 16 cryomodules, 14 for LCLS-II and 2 for LCLS-II HE tested at CMTF. The peak detuning, as well as the RMS detuning for each cryomodule, will be discussed. For each cryomodule, the data was taken with enough soaking time to prevent any thermalization effects which can show up in the detuning. Each data capture taken was 30 minutes or longer and sampled at 1 kHz.

Poster MOPA24 [1.428 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA24

About •

Received ※ 03 August 2022 — Revised ※ 10 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 20 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPA46

Cryogenic Dielectric Structure with GΩ/m Level Shunt Impedance

impedance, simulation, acceleration, accelerating-gradient

157

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA

Shunt impedance is one of the most important parameters characterizing particle acceleration efficiency. It is known that RF losses are reduced at cryogenic temperatures. For example, a record high shunt impedance of 350 MΩ/m was demonstrated recently for all metal X-band accelerating structure, which is more than 2 times higher than that at room temperature. In this article we present a novel hybrid dielectric structure which can achieve even higher shunt impedance due to the fact that losses in dielectric materials reduced much more than in pure copper.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA46

About •

Received ※ 12 August 2022 — Revised ※ 16 August 2022 — Accepted ※ 23 August 2022 — Issue date ※ 17 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUYD6

Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations

cathode, gun, electron, MMI

292

G.S. Gevorkyan, T.J. Hanks, A.H. Kachwala, S.S. Karkare, C.J. Knill, C.A. Sarabia Cardenas
Arizona State University, Tempe, USA

Funding: This work was supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams, and the DOE under Grant No. DE-SC0021092.
We present the first results of the commissioning of the 200 kV DC electron gun with a cryogenically cooled cathode at Arizona State University. The gun is specifically designed for studying a wide variety of novel cathode materials including single crystalline and epitaxially grown materials at 30 K temperatures to obtain the lowest possible intrinsic emittance of UED and XFEL applications [1]. We will present the measurements of the cryogenic performance of the gun and the first high voltage commissioning results.
[1] G. S. Gevorkyan et. al., Proc. of NAPAC19 MOPLM16 (2019)

Slides TUYD6 [12.632 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUYD6

About •

Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA80

Cyborg Beamline Development Updates

gun, cathode, cavity, simulation

512

G.E. Lawler, A. Fukasawa, N. Majernik, J.R. Parsons, J.B. Rosenzweig, Y. Sakai
UCLA, Los Angeles, California, USA
F. Bosco
Sapienza University of Rome, Rome, Italy
Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
B. Spataro
LNF-INFN, Frascati, Italy

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409.
Xray free electron laser (XFEL) facilities in their current form are large, costly to maintain, and inaccessible due to their minimal supply and high demand. It is then advantageous to consider miniaturizing XFELs through a variety of means. We hope to increase beam brightness from the photoinjector via high gradient operation (>120 MV/m) and cryogenic temperature operation at the cathode (<77K). To this end we have designed and fabricated our new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBGORG). The photogun is 0.5 cell so much less complicated than our eventual 1.6 cell photoinjector. It will serve as a prototype and test bed for cathode studies in a new cryogenic and very high gradient regime. We present here the fabricated structure, progress towards commissioning, and beamline simulations.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA80

About •

Received ※ 02 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 09 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA81

Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure

cavity, GUI, distributed, electron

516

G.E. Lawler, A. Fukasawa, J.R. Parsons, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
A. Mostacci
Sapienza University of Rome, Rome, Italy
E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
B. Spataro
LNF-INFN, Frascati, Italy

Funding: This work was supported by the DOE Contract DE-SC0020409.
High-gradient RF structures capable of maintaining gradients in excess of 250 MV/m are critical in several concepts for future electron accelerators. Concepts such as the ultra-compact free electron laser (UC-XFEL) and the Cool Copper Collider (C3) plan to obtain these gradients through the cryogenic operation (<77K) of normal conducting copper cavities. Breakdown rates, the most significant gradient limitation, are significantly reduced at these low temperatures, but the precise physics is complex and involves many interacting effects. High-power RF breakdown measurements at cryogenic temperatures are needed at the less explored C-band frequency (5.712 GHz), which is of great interest for the aforementioned concepts. On behalf of a large collaboration of UCLA, SLAC, LANL, and INFN, the first C-band cryogenic breakdown measurements will be made using a LANL RF test infrastructure. The 2-cell geometry designed for testing will be modifications of the distributed coupled reentrant design used to efficiently power the cells while staying below the limiting values of peak surface electric and magnetic fields.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA81

About •

Received ※ 29 July 2022 — Accepted ※ 02 August 2022 — Issue date ※ 08 August 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEZE4

First High-Gradient Results of UED/UEM SRF Gun at Cryogenic Temperatures

gun, cavity, SRF, accelerating-gradient

607

R.A. Kostin, C. Jing
Euclid Beamlabs, Bolingbrook, USA
D.J. Bice, T.N. Khabiboulline, S. Posen
Fermilab, Batavia, Illinois, USA

Funding: The project is funded by DOE SBIR #DE-SC0018621
Benefiting from the rapid progress on RF photogun technologies in the past two decades, the development of MeV range ultrafast electron diffraction/microscopy (UED and UEM) has been identified as an enabling instrumentation. UEM or UED use low power electron beams with modest energies of a few MeV to study ultrafast phenomena in a variety of novel and exotic materials. SRF photoguns become a promising candidate to produce highly stable electrons for UEM/UED applications because of the ultrahigh shot-to-shot stability compared to room temperature RF photoguns. SRF technology was prohibitively expensive for industrial use until two recent advancements: Nb₃Sn and conduction cooling. The use of Nb₃Sn allows to operate SRF cavities at higher temperatures (4K) with low power dissipation which is within the reach of commercially available closed-cycle cryocoolers. Euclid is developing a continuous wave (CW), 1.5-cell, MeV-scale SRF conduction cooled photogun operating at 1.3 GHz. In this paper, we present first high gradient results of the gun conducted in liquid helium.

Slides WEZE4 [2.817 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEZE4

About •

Received ※ 05 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 29 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA32

Spallation Neutron Source Cryogenic Moderator System Helium Gas Analysis System

MMI, neutron, operation, target

699

B. DeGraff, L. Pinion
ORNL RAD, Oak Ridge, Tennessee, USA
R. Armstrong, J. Denison, M.P. Howell, S.-H. Kim, D. Montierth
ORNL, Oak Ridge, Tennessee, USA
M.D. Williamson
LBNL, Berkeley, California, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) operates the Cryogenic Moderator System (CMS). The CMS comprises a 20-K helium refrigerator and three helium to hydrogen heat exchangers in support of hydrogen cooled spallation moderation vessels. This system uses vessels filled with activated carbon as the final major component to remove oil vapor from the compressed helium in the cryogenic cold box. SNS uses a LINDE multi-component gas analyzer to detect the presence of contaminants in the warm helium flow upstream of the cold box including aerosolized oil vapor. The design challenges of installing and operating this analyzer on the CMS system due to normal system operating pressures will be discussed. The design, fabrication, installation, commissioning, and initial results of this system operation will be presented. Future upgrades to the analyzer system will also be discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA32

About •

Received ※ 06 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 05 October 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA66

Near-Threshold Photoemission from Graphene Coated Cu Single Crystals

electron, cathode, experiment, brightness

776

C.J. Knill, S.S. Karkare
Arizona State University, Tempe, USA
H. Ago, K. Kawahara
Global Innovation Center, Kyushu University, Kasuga, Fukuoka, Japan
E. Batista, N.A. Moody, G.X. Wang, H. Yamaguchi, P. Yang
LANL, Los Alamos, New Mexico, USA

Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams, and by the Department of Energy under Grant DE-SC0021092.
The brightness of electron beams emitted from photocathodes plays a key role in the performance of x-ray free electron lasers (XFELs) and ultrafast electron diffraction (UED) experiments. In order to achieve the maximum beam brightness, the electrons need to be emitted from photocathodes with the smallest possible mean transverse energy (MTE). Recent studies have looked at the effect that a graphene coating has on the quantum efficiency (QE) of the cathode [1]. However, there have not yet been any investigations into the effect that a graphene coating has on the MTE. Here we report on MTE and QE measurements of a graphene coated Cu(110) single crystal cathode at room and cryogenic temperatures. At room temperature, a minimum MTE of 25 meV was measured at 295 nm. This MTE remained stable at 25 meV over several days. At 77 K, the minimum MTE of 9 meV was measured at 290 nm. We perform density functional theory (DFT) calculations to look at the effects of a graphene coating on a Cu(111) surface state. These calculations show that the graphene coating reduces the radius of the surface state, allowing for emission from a lower transverse energy state in comparison to bare Cu(111).
[1] F. Liu et al, Appl. Phys. Lett. 110, 041607 (2017); https://doi.org/10.1063/1.4974738

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA66

About •

Received ※ 28 July 2022 — Revised ※ 19 July 2022 — Accepted ※ 07 August 2022 — Issue date ※ 10 August 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYE4

Development of an Ultra-Low Vibration Cryostat Based on a Closed-Cycle Cryocooler

vacuum, radiation, instrumentation, synchrotron

874

R.W. Roca
Illinois Institute of Technology, Chicago, Illinois, USA
E.W. Knight, R.A. Kostin, Y. Zhao
Euclid TechLabs, Solon, Ohio, USA

Low temperature and low vibration cryostats are useful in a variety of applications such as x-ray diffraction, quantum computing, x-ray monochromators and cryo-TEMs. In this project, we explore an ultra-low vibration cryostat with the cooling provided by a closed cycle cryocooler. Closed-cycle cryocoolers inevitably introduce vibrations into the system, and in this project, flexible copper braiding was used to decouple vibrations and provide cooling at the same time. In order to develop the cryostat, capacity map of a two stage Sumitomo cryocooler was measured as well as vibration transmission through different copper braids using an IR interferometer. This paper covers the capacity map and vibration measurements in the first prototype.

Slides THYE4 [4.989 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYE4

About •

Received ※ 16 July 2022 — Revised ※ 10 August 2022 — Accepted ※ 20 August 2022 — Issue date ※ 12 September 2022

Cite •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)