The Heart of Our Detectors Multichannel Plate Operation

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Using Molecular Dissociation to Determine the
Efficiency of a Delay Line Microchannel-plate
Detector, a Progress Report
Bishwanath Gaire
A.M. Sayler, P.Q. Wang, Nora G. Johnson, M.
Leonard, E. Parke, K.D. Carnes, and I. Ben-Itzhak
Supported by the Chemical Sciences, Geosciences
and Biosciences Division, Office of Basic Energy
Sciences, Office of Science, U.S. Department of
Energy.
J.R. Macdonald Laboratory, Physics Department,
Kansas State University, Manhattan, Kansas 66506
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Motivation
Experimental set up using delay line detector for
laser-ion beam interactions
- Microchannel-plate delay line detector is being
used in coincidence imaging method
- We want check and improve the efficiency of
the detector for better rates
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Introduction
Microchannel-plate
- not detected
- detected
Electronic signal
Detection Efficiency
Probability for the detection of the electronic
pulse per incoming particle
Absolute and Relative (Effective)
B. Brehm et al., Meas. Sci. Technol. 6 (1995)
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Delay-line Timing Signals
All times recorded in a time-to-digital
converter on an event-by-event basis by computer.
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Method
- There are always two distinguishable hits on
the detector for one dissociation of a diatomic
molecular ion
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One and two dimensional TOF spectra
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Model
Dissociation of H2 H H
Measured quantities MHH, MH, MH
Unknowns eH, eH and NHH
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Efficiency
Total number of hits
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Two Channels
Laser used pulse width - 45 fs wavelength
-790nm
HD HD
HD HD
Measured Ms, unknowns es and Ns
Problem - Five equations - Six unknowns
- eH, eH, eD, eD -
NHD, N HD
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Assumption N HD N HD

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Results
-The measured efficiencies are of the order of 25
to 30 nearly half the open area ratio 40 to 50

Individual Signal Efficiency
- The left and right- position signals have
almost same efficiency
-The timing signal has lower efficiency
- Down-position signal has problem
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Summary
This method
-Simple and direct measurement of absolute
detection efficiency
- The signal which is less efficient can be
identified and improved
- Increase in efficiency will increase the rate
in our experiments
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Future plan
- Improvement for the timing and down-position
signal
- Measurement of position dependent efficiency
Dividing the detector into sectors and rings
O2 O O
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Thank You
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Why assumption NHD NHD ?
Explanation using dressed potential curves /
Floquet pictures
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Rotated and projected T1T2 Spectrum