Loss of Cavity Vacuum Experiment at CEBAF

Wiseman, M.; Crawford, K.; Drury, M.; Jordan, Kevin; Preble, J.; Saulter, Q.; Schneider, W.

doi:10.1007/978-1-4615-2522-6_121

Cited by 18 publications

(10 citation statements)

References 1 publication

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“…With similar steady film boiling temperatures, heat transfer rates in slight excess of 20 kW/m 2 have been reported [18]. This value also fits in the 18-28 kW/m 2 range obtained from the CEBAF loss of cavity vacuum experiment [1]. The Breen-Westwater correlation for large diameter tubes [19] with this steady film boiling condition predicts a heat transfer rate of 14.5 kW/m 2 .…”

Section: B Heat Transfer Estimatessupporting

confidence: 58%

“…The air will cryodeposit (solidify) on the channel walls and rapidly transfer heat to the helium bath. The potential severity of this accident drove several particle accelerator laboratories to conduct beam-line vacuum loss tests during the accelerator development stage [1], [2]. The general purpose of these tests is to verify the effectiveness of the pressure relief system foreseeing such an accident.…”

Section: Introductionmentioning

confidence: 99%

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Sudden Vacuum Loss in Long Liquid Helium Cooled Tubes

Dhuley

Sciver

2015

IEEE Trans. Appl. Supercond.

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Sudden vacuum loss in straight long tubes cooled by liquid helium is investigated. The scenario resembles an accident in a superconducting particle accelerator when the beam-cavity suddenly loses its vacuum to atmosphere. Following this accident, air will propagate down the vacuum channel and freeze on the cold walls. To warrant against catastrophes of this accident, it is vital to know the propagation speed of air in the vacuum space and the heat load on the helium bath. An experimental setup has been developed to determine these parameters. Experiments are conducted wherein a large nitrogen gas tank is rapidly vented to a high vacuum tube (∼10 −4 Pa) immersed in liquid helium at 4.2 K. The measurements comprise of the tube pressure to determine the propagation speed, the tank pressure to determine the gas mass flow rate into the tube, and the tube temperature to estimate the heat load. Flash solidification of the gas on the cold tube, which is apparent in the measurements, limits the propagation speed to the order of 10 m/s. Based on the mass flow measurement a heat deposition rate of 60 kW/m 2 on the vacuum tube is estimated, while the heat transfer rate to the helium bath is predicted to exceed 20 kW/m 2 .

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Section: B Heat Transfer Estimatessupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Sudden Vacuum Loss in Long Liquid Helium Cooled Tubes

Dhuley

Sciver

2015

IEEE Trans. Appl. Supercond.

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“…Previous work on SLV failure in SRF systems has focused on quantifying the heat flux from air condensation on the LHe vessel(s), with mean heat fluxes largely on the order of 1 -4 W*cm -2 [1][2][3][4]. Most relevant to the present experiment is a SLV failure experiment performed by the German Electron-Synchrotron (DESY) of a XFEL cryomodule consisting of 1.3 GHz elliptical cavities similar to what is proposed for Project X.…”

Section: Introductionmentioning

confidence: 99%

Results from sudden loss of vacuum on scaled superconducting radio frequency cryomodule experiment

Dalesandro¹,

Dhuley²,

Theilacker³

et al. 2014

AIP Conference Proceedings

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Abstract. Superconducting radio frequency (SRF) cavities for particle accelerators are at risk of failure due to sudden loss of vacuum (SLV) adjacent to liquid helium (LHe) spaces. To better understand this failure mode and its associated risks an experiment is designed to test the longitudinal effects of SLV within the beam tube of a scaled SRF cryomodule that has considerable length relative to beam tube cross section. The scaled cryomodule consists of six individual SRF cavities each roughly 350 mm long, initially cooled to 2 K by a superfluid helium bath and a beam tube pumped to vacuum. A fast-acting solenoid valve is used to simulate SLV on the beam tube, from which point it takes over 3 s for the beam tube pressure to equalize with atmosphere, and 30 s for the helium space to reach the relief pressure of 4 bara. A SLV longitudinal effect in the beam tube is evident in both pressure and temperature data, but interestingly the temperatures responds more quickly to SLV than do the pressures. It takes 500 ms (roughly 100 ms per cavity) for the far end of the 2 m long beam tube to respond to a pressure increase compared to 300 ms for temperature (approximately 50 ms per cavity). The paper expands upon these and other results to better understand the longitudinal effect for SRF cryomodules due to SLV.

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“…This translates to a propagation speed of about 3 m/s. The delayed effect has also been observed during a vacuum break study at CEBAF [5]. Very recently Dalesandro et al [6] conducted a detailed experiment to measure this propagation.…”

Section: Introductionmentioning

confidence: 74%