Title: Performance of microchannel plate based detectors for <25 keV x rays: Monte Carlo simulations and comparisons with experimental results

Abstract

We present the results of Monte Carlo simulations of the microchannel plate (MCP) response to x rays in the 250 eV to 25 keV energy range as a function of both x-ray energy and impact angle and their comparisons with the experimental results from the X8A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory. Incoming x rays interact with the lead glass of the microchannel plate, producing photoelectrons. Transport of the photoelectrons is neglected in this model, and it is assumed that photoelectrons deposit all their energy at the point they are created. This deposition leads to the generation of many secondary electrons, some fraction of which diffuse to the MCP pore surface where they can initiate secondary electron cascades in the pore under an external voltage bias. X-ray penetration through multiple MCP pore walls is increasingly important above 5 keV, and the effect of this penetration on MCP performance is studied. In agreement with past measurements, we find that the dependence of MCP sensitivity with angle relative to the pore bias changes from a cotangent dependence to angular independence and then proceeds to a secant dependence as the x-ray energy increases. We also find that withmore » the increasing x-ray energy, the MCP gain sensitivity as a function of bias voltage decreases. The simulations also demonstrate that for x rays incident normal to the MCP surface, spatial resolution shows little dependence on the x-ray energy but degrades with the increasing x-ray energy as the angle of incidence relative to the surface normal increases. This agrees with experimental measurements. Simulation studies have also been completed for MCPs gated with a subnanosecond voltage pulse. In this work, we find that the optical gate profile width increases as the x-ray energy is increased above 5 keV, a consequence of increased x-ray penetration at energies >5 keV. Simulations of the pulsed dynamic range show that the dynamic range varies between ~100 and 1000 depending on x-ray energy and peak voltage.« less

Authors:

Kruschwitz, Craig A. ^[1]; Wu, Ming  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-0515-6464"

Moy, Ken  ^[3]

• Search DOE PAGES for author "Moy, Ken"
• Search DOE PAGES for ORCID "0000-0003-2888-3370"

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+ Show Author Affiliations

1. Nevada National Security Site (NNSS), Los Alamos, NV (United States). New Mexico Operations; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
3. Nevada National Security Site, Santa Barbara, CA (United States). Special Technologies Laboratory

Publication Date:

Thu Apr 01 00:00:00 EDT 2021

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nevada National Security Site/Mission Support and Test Services LLC (NNSS/MSTS), North Las Vegas, NV (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP)

OSTI Identifier:

1781537

Alternate Identifier(s):

OSTI ID: 1773562

Report Number(s):

SAND-2020-10815J; DOE/NV/03624-0813
Journal ID: ISSN 0034-6748; 691312; TRN: US2210299

Grant/Contract Number:  

AC04-94AL85000; NA0003624; NA0003525; DENA-0003525

Resource Type:

Accepted Manuscript

Journal Name:

Review of Scientific Instruments

Additional Journal Information:

Journal Volume: 92; Journal Issue: 4; Journal ID: ISSN 0034-6748

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

47 OTHER INSTRUMENTATION; Monte Carlo methods; Synchrotron radiation; High-energy X rays; Quantum efficiency; Computer simulation; Microchannel plate detectors