Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Mu2e Straw Tube Tracker Gas Flow Quality Control

Vishal Bharatwaj, Scott N. Israel, Mamta Jangra, Minh Truong Nguyen, Joey Peck, Matthew Stortini, Nam H. Tran, Dan Ambrose, Andrew Edmonds, Hannah Hass, Emma R. Martin, Aseet Mukherjee, Klara Northrup, James L. Popp, Vadim L. Rusu, Robert S. Tschirhart, Robert L. Wagner

TL;DR

The paper presents a gas-flow quality-control method for the Mu2e straw-tube tracker that uses time-dependent current measurements from a $^{55}$Fe source during gas exchange to quantify the onset of ionization gain, linking rise time to straw conductance. The method employs an Ar-CO2 (80:20) fill displaced by N2, analyzes per-doublet rise time $\Delta t$ and peak gain via Gaussian and error-function fits, and flags flow-restricted doublets for repair. Applied to 11,280 doublets over two years, it identified 219 flow restrictions (1.94%), with 164 restored (74.9%) after repairs; at the single-straw level, 0.95% were blocked, with 76.3% recoveries. The resulting uniform gas flow improves tracker performance and the approach is adaptable to other gaseous detectors requiring high-channel-count screening and quality control.

Abstract

We present a tracker gas flow quality control method developed for the Mu2e straw tube tracker. Using time-dependent current measurements, we quantify the onset time of ionization gain induced by an 55Fe source during gas exchange, which is correlated to the gas conductance in the straw. This allows for the identification of channels with inadequate flow. This approach is broadly applicable to other gaseous detectors that require high-channel-count screening.

Mu2e Straw Tube Tracker Gas Flow Quality Control

TL;DR

The paper presents a gas-flow quality-control method for the Mu2e straw-tube tracker that uses time-dependent current measurements from a Fe source during gas exchange to quantify the onset of ionization gain, linking rise time to straw conductance. The method employs an Ar-CO2 (80:20) fill displaced by N2, analyzes per-doublet rise time and peak gain via Gaussian and error-function fits, and flags flow-restricted doublets for repair. Applied to 11,280 doublets over two years, it identified 219 flow restrictions (1.94%), with 164 restored (74.9%) after repairs; at the single-straw level, 0.95% were blocked, with 76.3% recoveries. The resulting uniform gas flow improves tracker performance and the approach is adaptable to other gaseous detectors requiring high-channel-count screening and quality control.

Abstract

We present a tracker gas flow quality control method developed for the Mu2e straw tube tracker. Using time-dependent current measurements, we quantify the onset time of ionization gain induced by an 55Fe source during gas exchange, which is correlated to the gas conductance in the straw. This allows for the identification of channels with inadequate flow. This approach is broadly applicable to other gaseous detectors that require high-channel-count screening.

Paper Structure

This paper contains 7 sections, 9 figures.

Table of Contents

  1. Introduction
  2. The Mu2e Tracker Panel Test Setup
  3. Straw Tube Gas Flow Quality Control
  4. Data Analysis Method
  5. Evaluating Results
  6. Conclusion
  7. Acknowledgments

Figures (9)

  • Figure 1: Overview of a panel test setup. (a) Photo showing the temporary cover with the auxiliary valve on the inlet side, the Digital Mother Board for data acquisition, and current amplifiers on the outlet side. (b) Illustration of the gas flow pattern. The design pattern, with the auxiliary valve closed, is indicated by green arrows. The valve pattern, with the auxiliary valve open, is shown using red arrows.
  • Figure 2: Illustrations of straw tubes. (a) Section view of the straw tube layout with measurements shown in millimeters. (b) A Straw doublet connected to a current amplifier. The cathode, consisting of aluminized Mylar straw tubes and their electrical connections, is shown in blue. The anode wires are red. The flow channels are represented by the two white regions at the ends of the straws. The straw and wire ends are supported by the solid green and black structures shown. The actual terminations do not appear here. The purple box contains the high-voltage supply and current amplifier.
  • Figure 3: Example current data from a straw doublet during a rise time study. (a) Raw current data shown in red. (b) Smoothed current data shown in green.
  • Figure 4: Measurements of Gaussian peaks for two source passes in a doublet. The green line represents smoothed data, the red line displays processed data, and the blue point marks the current peak value.
  • Figure 5: Processed data for one test run of one doublet. The blue points correspond to each peak, as measured in the Gaussian fit. The red line is an error function fit to the region of rising current. The violet line indicates when the auxiliary valve is closed at $t_0$, and the green line marks when the measured current reaches 90$\%$ of the fit maximum at $t_1$. The difference between these represents the rise time, $\Delta t$.
  • ...and 4 more figures