HRC-I QE measurements

1  Introduction

During October 1996 the HRC IPI team performed a series of QE measurements on what was considered at the time to be the HRC-I flight unit. This assembly consisted of a CsI coated MCP stack from GEOC (SN 94M0051-23 and 94M0051-28) and an Al/polyimide/C UV/ion shield (Luxel SN 010). During November 1996, the UV/ion shield was found to be too transmitting in the FUV and was replaced. The MCPs also developed a dead spot in the central portion and as a result were also replaced. The new MCP stack was also from GEOC and CsI coated (SN 94M0051-17 and 94M0051-19). The UV/ion shield was Al coated polyimide (Luxel SN 016). QE measurements were performed on this assembly in late November. This memo is a presentation of the first look at the QE vs energy in the ``sweet spot'' of the HRC-I.

2  Measurement Setup and Procedure

The QE measurements described here were all performed on Pipe #1 in the HRC lab in Porter Exchange. The laboratory set-up and procedures are described in detail in ref [1]; the following is a summary. The HRC-I assembly was mounted on rotational stages in a vacuum chamber at the opposite end of the x-ray pipe from the x-ray source. The source to MCP distance was ~ 705 cm. A gas flow proportional counter, referred to as the BND, was also installed in the chamber with the MCPs. At the source end of the pipe, a second gas flow proportional counter, referred to as the Monitor, was mounted on a short arm perpendicular to the pipe. Sets of filters could be inserted between the source and the pipe and between the source and the Monitor.

The BND and the MCPs were never operated simultaneously, so as to avoid the possibility that a BND window leak would cause a break-down that would damage the MCPs. A QE measurement would start with the MCP HV turned off and the BND and Monitor both filled with gas. The x-ray source would be turned on and operating HV set for both the BND and Monitor. Pulse height distributions would then collected simultaneously from the BND and Monitor. The x-ray source would then be shut off and simultaneous background pulse height distributions collected from the BND and Monitor. The BND HV would then be turned off and the gas pumped out; the Monitor was left on. The MCP HV was then turned on and simultaneous backgrounds collected with the HRC-I assembly and the Monitor. Finally, the x-ray source would be turned on and data collected from the HRC-I assembly and the Monitor.

3  Data Reduction

The QE of the HRC-I is calculated by comparing the rate in the HRC-I to that in the BND, which has a known QE:

QE_HRC is the HRC-I QE

QE_BND is the QE of the BND

R_HRC is the net rate due to the source in the HRC-I

W_HRC is the solid angle subtended by the HRC-I region

R_BND is the net rate due to the source in the BND

W_BND is the solid angle subtended by the BND

R_MonBND is the net rate in the Monitor during the BND observation

R_MonHRC is the net rate in the Monitor during the HRC observation

3.1  MCP Data

3.2  BND Data

3.3  Monitor Data

4  Results

References

[1]

P-HRC-302 Rev. A, ``Verification Test Procedure for the HRC Imaging Detector'', 27 September 1996.

Dr. Michael Juda
Harvard-Smithsonian Center for Astrophysics
60 Garden Street, Mail Stop 70
Cambridge, MA 02138, USA
Ph.: (617) 495-7062
Fax: (617) 495-7356
E-mail: mjuda@cfa.harvard.edu