Measurement of longitudinal electron diffusion in liquid argon

Abstract

We report the measurement of longitudinal electron diffusion coefficients in liquid argon for electric fields between 100 and 2000 V/cm with a gold photocathode as a bright electron source. The measurement principle, apparatus, and data analysis are described. In the region between 100 and 350 V/cm, our results show a discrepancy with the previous measurement [1]. In the region between 350 and 2000 V/cm, our results represent the world's best measurement. Over the entire measured electric field range, our results are systematically higher than the calculation of Atrazhev-Timoshkin [2]. The quantum efficiency of the gold photocathode, the drift velocity and longitudinal diffusion coefficients in gas argon are also presented.

A 20-liter test stand with gas purification for liquid argon research

“…The decline of QE at higher fields in our setup is presumably due to the decreasing transparency of the grid (absent in the results from Ref. [12]) as the drift field increases. As shown in Sec.…”

“…A drift stack has been constructed for the electron transport properties measurements, which is an improved version of the drift stack described previously in Ref. [12]. The field uniformity has been improved by a redesign of the rings and the cathode holder, and the charge noise has been reduced by integrating the pre-amplifier into the anode board and operating it in the LAr.…”

“…The results in Ref. [12] were obtained under two significantly different conditions: the entire setup is baked up to ∼ 90 • C and pumped to ∼ 10 −8 Torr, and the electron current measured is leaving the cathode. Since our main 20-liter dewar is vacuum insulated, no significant baking procedure is practical.…”

“…It is an upgrade of a liquid argon test stand reported in Ref. [12], providing better thermal stability and an improved drift stack apparatus. This paper is organized as follows.…”

Electron transport and electric field simulations in two-phase detectors with THGEM electrodes

“…The global fit of electron mobility reported in [24] was used for our simulations up to 2 kV/cm and the data of [27] above. For the details on diffusion coefficients and mobility of electrons in liquid argon the reader is referred to [24].…”