1. 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

2. Motivation
Experimental set up using delay line detector for laser-ion beam interactions
H2+ Beam
Faraday Cup
Delay Line Detector
Spectrometer
Laser focus VS H+ H
(x1, y1, t1)
(x2, y2, t2)
- 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

3. Introduction Microchannel-plate Detection Efficiency
- 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)

4. Delay-line Timing Signals
All times recorded in a
time-to-digital converter
on an event-by-event
basis by computer.

5. Method
- There are always two distinguishable hits on the detector for one dissociation of a diatomic molecular ion

6. One and two dimensional TOF spectra

7. Model Dissociation of H2+ H + H+ Measured quantities MH+H+, MH, MH+
Unknowns eH, eH+ and NH+H+

8. Efficiency
Total number of hits

9. HD+ H+D+ HD+ H++D - eH, eH+, eD, eD+ Two Channels
Laser used
pulse width - 45 fs
wavelength -790nm
HD H+D+
HD H++D
Measured M’s, unknowns e’s and N’s
Problem - Five equations
- Six unknowns
- eH, eH+, eD, eD+
- NH+D+, N H++D

10. Assumption N H++D = N H+D+

11. 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

12. 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

13. Future plan
- Improvement for the timing and down-position signal
- Measurement of position dependent efficiency
Dividing the detector into sectors and rings
O O + O+

14. Thank You

15. Why assumption NH++D= NH+D+ ?
Explanation using dressed potential curves / Floquet pictures

16. Rotated and projected T1T2 Spectrum