Effects of thermal acoustic oscillations on LCLS-II cryomodule testing

Hansen, Benjamin; Atassi, O Al; Bossert, R.; Einstein-Curtis, Joshua; Holzbauer, Jeremiah; Hughes, William H; Hurd, J.W.; Kaluzny, Joshua; Klebaner, Arkadiy; Makara, J.; Pischalnikov, Y.; Schappert, W.; Stanek, R.; Theilacker, J.; Wang, R; White, Michael J.

doi:10.1088/1757-899x/278/1/012188

Cited by 4 publications

(3 citation statements)

References 5 publications

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“…It soon became obvious that the ice formation on the VLP return valves is due to thermo-acoustic oscillations (TAO), a phenomenon well known in cryogenic installations and described in many publications as for instance in [6]. In case of the ESS is that the CDS-EL VLP return valves are relatively large with a gap between valve body and valve insert of 2 mm that for this DN50 valve results in a residual cross section of ~500 mm 2 , the equivalent of a DN 20 tube, for the gas to travel between the cold and the warm end.…”

Section: St Cooldown and Discovery Of Issues On Control Valvesmentioning

confidence: 99%

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Commissioning of the cryogenic distribution system of the ESS superconducting linac

Arnold,

Asensi,

Elias

et al. 2024

IOP Conf. Ser.: Mater. Sci. Eng.

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The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration in Lund, Sweden. An essential part of the project is the linear 2.0 GeV proton accelerator. Its superconducting part is designed to comprise 13 spoke and 30 elliptical cryomodules that are cooled at 2K. The cryogenic distribution system (CDS) connects the refrigeration plant with the cryomodules via multi-transfer lines, individual valveboxes for every cryomodule and an endbox. It is designed, manufactured and installed under the responsibility of two ESS in-kind partners. The CDS for the spoke cryomodules (CDS-SL) is supplied by IJCLab, France, the CDS for the elliptical cryomodules (CDS-EL) is supplied by WUST, Poland. Pre-commissioning, commissioning and operation is done by ESS whereby IFJ PAN contributed with valuable advice. Pre-commissioning activities like loop checks, temperature curve validation, pressure sensor calibration or valve initialization and leak tightness tests followed after mechanical or electrical completion of the respective CDS parts and started in summer 2022. Eventually, the system was ready for commissioning and a first cooldown was performed in December 2022. Goal of this commissioning was to acceptance test and check off the system before pilot cryomodule installation in the tunnel started in March 2023. The paper describes diverse challenges regarding TAO and cryo operation. Test results, lessons learnt, and required modifications are discussed as well as preliminary results of retesting and an outlook.

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Section: St Cooldown and Discovery Of Issues On Control Valvesmentioning

confidence: 99%

“…Inspired by [6] we looked into attaching convection brakes, so called wipers, along the valve stems of the VLP return valves. Anchoring the valves properly to the thermal shield would require opening of all fully welded CDS-EL VBXs and not guarantee the complete elimination of TAO.…”

Section: Rectification and System Modificationsmentioning

confidence: 99%

Commissioning of the cryogenic distribution system of the ESS superconducting linac

Arnold,

Asensi,

Elias

et al. 2024

IOP Conf. Ser.: Mater. Sci. Eng.

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“…This mechanism of vibrations was first observed in the LCLS-II cryomodules while testing at Fermilab. [31] Following discussions with the Fermilab team, we inserted sleeves made of a cryogenic compatible PEEK plastic material on the stem to restrict the gas flow and suppress vibrations. [32] Table I shows a summary of the microphonics measurements on all cavities in different configurations of the cryogenic system.…”

Section: A Passive Suppressionmentioning

confidence: 99%

Active suppression of microphonics detuning in high QL cavities

Banerjee

Hoffstaetter

Liepe

et al. 2019

Phys. Rev. Accel. Beams

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Operation of Superconducting Radio Frequency (SRF) cavities with high loaded quality factors is becoming increasingly preferred for applications which involve low beam loading including Energy Recovery Linacs (ERL). Vibration induced microphonics detuning poses a major operational bottleneck in these low bandwidth systems, adversely affecting field stability. Besides passive measures of mitigating the vibration sources, modern SRF cavities are also attached to fast tuners incorporating piezo-electric actuators. We demonstrate the narrow band active noise control algorithm for realizing active resonance control and propose a modification based on the Least Mean Square approach to adaptively tune the control parameters and study it's stability and performance. We discuss our experience of using passive mitigation techniques while commissioning the Main Linac Cryomodule of the Cornell-BNL ERL Test Accelerator (CBETA) and report a net reduction in peak detuning by more than a factor of 2 in its unstiffened cavities. Finally, we demonstrate stable performance of our resonance control system with consistent reduction of peak microphonics detuning by almost a factor of 2 on multiple cavities.

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