The Qweak high performance LH2 target

J. Brock; S. Covrig Dusa; J. A. Dunne; C. Keith; D. Meekins; J. Pierce; G. R. Smith; A. Subedi

doi:10.1016/j.nima.2023.168316

The Q_weak high performance LH₂ target

J. Brock, S. Covrig Dusa, J. A. Dunne, C. Keith, D. Meekins, J. Pierce, G. R. Smith, A. Subedi

Research output: Contribution to journal › Article › peer-review

Abstract

A high-power liquid hydrogen target was built for the Jefferson Lab Q_weak experiment, which measured the tiny parity-violating asymmetry in e→p scattering at an incident energy of 1.16 GeV, and a Q²=0.025 GeV². To achieve the luminosity of 1.7×10³⁹ cm⁻² s⁻¹, a 34.5 cm-long target was used with a beam current of 180 μA. The ionization energy-loss deposited by the beam in the target was 2.1 kW. The target temperature was controlled to within ±0.02 K and the target noise (density fluctuations) near the experiment's beam helicity-reversal rate of 960 Hz was only 53 ppm. The 58 liquid liter target achieved a differential pressure (head) across the pump of 7.6 kPa (11.4 m) and a mass flow of 1.2 ± 0.3 kg/s (corresponding to a volume flow of 17.4 ± 3.8 l/s) at the nominal 29 Hz rotation frequency of the recirculating centrifugal pump. We describe aspects of the design, operation, and performance of this target, the highest power LH₂target ever used in an electron scattering experiment to date.

Original language	English
Article number	168316
Journal	Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume	1053
DOIs	https://doi.org/10.1016/j.nima.2023.168316
State	Published - Aug 2023
Externally published	Yes

Funding

This work was supported by DOE contract No. DE-AC05-06OR23177 , under which Jefferson Science Associates, LLC operates Thomas Jefferson National Accelerator Facility. Construction and operating funding for the target was provided through the US Department of Energy (DOE) . We gratefully acknowledge help from JLab designers R. Anumagalla, B. Metzger, P. Medeiros, S. Furches, and G. Vattelana. The authors thank the Dept. of Physics at the Univ. of New Hampshire and Prof. F. William Hersman in particular for support with the Fluent license during the design of the target with CFD. We are also indebted to JLab engineers P. Brindza, D. Young, J. Henry, E. Daly, K. Dixon, R. Ganni, and P. Knudson for useful discussions, the technical staff of Hall C and the JLab target group, and software expert S. Witherspoon for her support helping us control our many devices. We are also grateful to P. Degtiarenko for simulations that helped us reduce the radiation from the target, as well as D. Hamlette and the other members of the radiation control group at JLab who helped make operation of the target possible. Finally, we thank J. Mei, J. Mammei, and all the members of the collaboration who operated the target during the experiment. This work was supported by DOE contract No. DE-AC05-06OR23177, under which Jefferson Science Associates, LLC operates Thomas Jefferson National Accelerator Facility. Construction and operating funding for the target was provided through the US Department of Energy (DOE) . We gratefully acknowledge help from JLab designers R. Anumagalla, B. Metzger, P. Medeiros, S. Furches, and G. Vattelana. The authors thank the Dept. of Physics at the Univ. of New Hampshire and Prof. F. William Hersman in particular for support with the Fluent license during the design of the target with CFD. We are also indebted to JLab engineers P. Brindza, D. Young, J. Henry, E. Daly, K. Dixon, R. Ganni, and P. Knudson for useful discussions, the technical staff of Hall C and the JLab target group, and software expert S. Witherspoon for her support helping us control our many devices. We are also grateful to P. Degtiarenko for simulations that helped us reduce the radiation from the target, as well as D. Hamlette and the other members of the radiation control group at JLab who helped make operation of the target possible. Finally, we thank J. Mei, J. Mammei, and all the members of the Qweak collaboration who operated the target during the experiment.

Funders	Funder number
CFD
Dept. of Physics
U.S. Department of Energy	DE-AC05-06OR23177
Thomas Jefferson National Accelerator Facility

Keywords

Density fluctuations
Electron scattering
Liquid hydrogen target
Parity-violation

Access to Document

10.1016/j.nima.2023.168316

Cite this

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title = "The Qweak high performance LH2 target",

abstract = "A high-power liquid hydrogen target was built for the Jefferson Lab Qweak experiment, which measured the tiny parity-violating asymmetry in e→p scattering at an incident energy of 1.16 GeV, and a Q2=0.025 GeV2. To achieve the luminosity of 1.7×1039 cm−2 s−1, a 34.5 cm-long target was used with a beam current of 180 μA. The ionization energy-loss deposited by the beam in the target was 2.1 kW. The target temperature was controlled to within ±0.02 K and the target noise (density fluctuations) near the experiment's beam helicity-reversal rate of 960 Hz was only 53 ppm. The 58 liquid liter target achieved a differential pressure (head) across the pump of 7.6 kPa (11.4 m) and a mass flow of 1.2 ± 0.3 kg/s (corresponding to a volume flow of 17.4 ± 3.8 l/s) at the nominal 29 Hz rotation frequency of the recirculating centrifugal pump. We describe aspects of the design, operation, and performance of this target, the highest power LH2target ever used in an electron scattering experiment to date.",

keywords = "Density fluctuations, Electron scattering, Liquid hydrogen target, Parity-violation",

author = "J. Brock and Dusa, {S. Covrig} and Dunne, {J. A.} and C. Keith and D. Meekins and J. Pierce and Smith, {G. R.} and A. Subedi",

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year = "2023",

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doi = "10.1016/j.nima.2023.168316",

language = "English",

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T1 - The Qweak high performance LH2 target

AU - Brock, J.

AU - Dusa, S. Covrig

AU - Dunne, J. A.

AU - Keith, C.

AU - Meekins, D.

AU - Pierce, J.

AU - Smith, G. R.

AU - Subedi, A.

PY - 2023/8

Y1 - 2023/8

N2 - A high-power liquid hydrogen target was built for the Jefferson Lab Qweak experiment, which measured the tiny parity-violating asymmetry in e→p scattering at an incident energy of 1.16 GeV, and a Q2=0.025 GeV2. To achieve the luminosity of 1.7×1039 cm−2 s−1, a 34.5 cm-long target was used with a beam current of 180 μA. The ionization energy-loss deposited by the beam in the target was 2.1 kW. The target temperature was controlled to within ±0.02 K and the target noise (density fluctuations) near the experiment's beam helicity-reversal rate of 960 Hz was only 53 ppm. The 58 liquid liter target achieved a differential pressure (head) across the pump of 7.6 kPa (11.4 m) and a mass flow of 1.2 ± 0.3 kg/s (corresponding to a volume flow of 17.4 ± 3.8 l/s) at the nominal 29 Hz rotation frequency of the recirculating centrifugal pump. We describe aspects of the design, operation, and performance of this target, the highest power LH2target ever used in an electron scattering experiment to date.

AB - A high-power liquid hydrogen target was built for the Jefferson Lab Qweak experiment, which measured the tiny parity-violating asymmetry in e→p scattering at an incident energy of 1.16 GeV, and a Q2=0.025 GeV2. To achieve the luminosity of 1.7×1039 cm−2 s−1, a 34.5 cm-long target was used with a beam current of 180 μA. The ionization energy-loss deposited by the beam in the target was 2.1 kW. The target temperature was controlled to within ±0.02 K and the target noise (density fluctuations) near the experiment's beam helicity-reversal rate of 960 Hz was only 53 ppm. The 58 liquid liter target achieved a differential pressure (head) across the pump of 7.6 kPa (11.4 m) and a mass flow of 1.2 ± 0.3 kg/s (corresponding to a volume flow of 17.4 ± 3.8 l/s) at the nominal 29 Hz rotation frequency of the recirculating centrifugal pump. We describe aspects of the design, operation, and performance of this target, the highest power LH2target ever used in an electron scattering experiment to date.

KW - Density fluctuations

KW - Electron scattering

KW - Liquid hydrogen target

KW - Parity-violation

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