Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

A cryogenic buffer gas beam source with in-situ ablation target replacement

Zhen Han, Zack Lasner, Collin Diver, Peiran Hu, Takahiko Masuda, Xing Wu, Ayami Hiramoto, Maya Watts, Satoshi Uetake, Koji Yoshimura, Xing Fan, Gerald Gabrielse, John M. Doyle, David DeMille

Abstract

The design and performance of a cryogenic buffer gas beam (CBGB) source with a load-lock system is presented. The ACME III electron electric dipole moment (eEDM) search experiment uses this source to produce a beam of cold, slow thorium monoxide (ThO) molecules. A key feature of the apparatus is its capability to replace ablation targets without interrupting vacuum or cryogenic conditions, increasing the average signal in the eEDM search. The source produces approximately $1.3 \times 10^{11}$ ground-state ThO molecules per pulse, with a rotational temperature of $4.8$ K, molecular beam solid angle of $0.31$ sr, and forward velocity of $200$ m/s. These parameters match the performance of traditional sources that require time-consuming thermal cycles for target replacement. A long-term yield improvement of about 40% is achieved when the load-lock system is used to replace targets biweekly.

A cryogenic buffer gas beam source with in-situ ablation target replacement

Abstract

The design and performance of a cryogenic buffer gas beam (CBGB) source with a load-lock system is presented. The ACME III electron electric dipole moment (eEDM) search experiment uses this source to produce a beam of cold, slow thorium monoxide (ThO) molecules. A key feature of the apparatus is its capability to replace ablation targets without interrupting vacuum or cryogenic conditions, increasing the average signal in the eEDM search. The source produces approximately ground-state ThO molecules per pulse, with a rotational temperature of K, molecular beam solid angle of sr, and forward velocity of m/s. These parameters match the performance of traditional sources that require time-consuming thermal cycles for target replacement. A long-term yield improvement of about 40% is achieved when the load-lock system is used to replace targets biweekly.
Paper Structure (11 sections, 2 equations, 6 figures)

This paper contains 11 sections, 2 equations, 6 figures.

Table of Contents

  1. Introduction
  2. Experiment Setup
  3. Cryogenic Buffer Gas Beam Source
  4. Load‐Lock System
  5. Detection Setup
  6. Measurement Results
  7. Cryogenic Temperatures
  8. Beam Properties
  9. Long-term yield improvement
  10. Conclusion
  11. acknowledgments

Figures (6)

  • Figure 1: (a) ACME III CBGB with load-lock system. (b) Unused ThO$_{2}$ ablation target. (c) ThO$_{2}$ ablation target after $\sim30$ days of continuous use.
  • Figure 2: (a) Diagram of the ACME III beam box. (b) Section through the buffer gas cell. (c) Setup for characterizing beam properties using absorption spectroscopy and precession phase measurement.
  • Figure 3: (a) Diagram of the load-lock system. The side panel of the beam box vacuum chamber, radiation shield and cryo-pumping shield on the side of load-lock system are not shown. Manipulators in the vertical assembly, including the magnetically coupled feedthrough and vertical tool rod (light green), transfer the target from the load-lock chamber (dark green) into the CBGB without breaking the vacuum and cryogenic environment. The horizontal assembly, which consists of a ferro-magnetic fluid rotary feedthrough and horizontal tool rod (cyan), 2-axis tilt stage (dark blue) and bellows sealed linear actuator (blue), serves to install the target into the cell. (b) Tips for vertical tool rod (light green) and horizontal tool rod (cyan). (c)-(f) Steps of transferring and installing the target plate onto the buffer gas cell. (g) Sliding door for blocking black-body radiation onto the cryo-pumping shields.
  • Figure 4: Temperatures of the cryogenic system during (a) removal of the target plate from the cell using the load lock system (b) installation of a room-temperature target plate directly onto the cell at cryogenic temperature using the load lock system. The cryopump cryocooler second stage is thermally connected to the 4K cryopumping shields, and the cell cryocooler second stage is connected to the buffer gas cell. Temperatures are measured using silicon diode sensors mounted on the cryocooler stages.
  • Figure 5: (a) A typical absorption measurement at a flow rate of 40. (b) Population distribution for different rotational levels. (c) Forward velocity distribution measured with clean cell and dusty cell. The vertical dashed lines represent the mean values of the distributions.
  • ...and 1 more figures