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

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

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)

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

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

One and two dimensional TOF spectra

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

Efficiency Total number of hits

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

Assumption N H++D = N H+D+

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

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

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+

Thank You

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

Rotated and projected T1T2 Spectrum