Paper | Title | Other Keywords | Page |
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MOPA24 | LCLS-II and HE Cryomodule Microphonics at CMTF at Fermilab | cavity, cryomodule, SRF, niobium | 103 |
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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. | |||
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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 | ||
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MOPA46 | Cryogenic Dielectric Structure with GΩ/m Level Shunt Impedance | impedance, simulation, acceleration, accelerating-gradient | 157 |
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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 | ||
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TUYD6 | Design of a 200 kV DC Cryocooled Photoemission Gun for Photocathode Investigations | cathode, gun, electron, MMI | 292 |
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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) |
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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 | ||
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TUPA80 | Cyborg Beamline Development Updates | gun, cathode, cavity, simulation | 512 |
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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. |
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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 | ||
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TUPA81 | Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure | cavity, GUI, distributed, electron | 516 |
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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. |
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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 | ||
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WEZE4 | First High-Gradient Results of UED/UEM SRF Gun at Cryogenic Temperatures | gun, cavity, SRF, accelerating-gradient | 607 |
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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. |
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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 | ||
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WEPA32 | Spallation Neutron Source Cryogenic Moderator System Helium Gas Analysis System | MMI, neutron, operation, target | 699 |
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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. |
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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 | ||
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WEPA66 | Near-Threshold Photoemission from Graphene Coated Cu Single Crystals | electron, cathode, experiment, brightness | 776 |
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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 |
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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 | ||
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THYE4 | Development of an Ultra-Low Vibration Cryostat Based on a Closed-Cycle Cryocooler | vacuum, radiation, instrumentation, synchrotron | 874 |
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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. | |||
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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 | ||
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