MRPC prototyping for NeuLAND and tests using the single electron mode of ELBE/Dresden

1. MRPC prototyping for NeuLAND and tests using the single electron mode of ELBE/Dresden Dmitry Yakorev, Daniel Bemmerer, Zoltan Elekes, Mathias Kempe1, Daniel Stach and Andreas Wagner R3B Collaboration meeting on technical issues, Darmstadt 14.-16.04.2010

2. Some details on the prototypes (built at FZD and at GSI) Design questions addressed: • Number of gaps: 2x2, 2x3, 2x4 • Strip size: (1.2-2.5) x 40 cm • Glass thickness: 0.55/1.0 mm • Interstrip spacing: 0.3, 0.6, 1.6, 3 mm • Semiconductive materials: One side semiconductive mylar film, acrylic paint, Licron spray • Readout with impedance matching transformers • Single-ended and differential readout: FOPI, PADI, ALICE FEC.

3. Experimental Cave Experimental setup, MRPC test station at ELBE/Dresden Measurement of time with reference to RF from ELBE linac, scintillators only for coincidence (trigger). MRPC can be moved remotely, 50cm in x and y direction

4. MRPC detector tests at ELBE Dresden ELBE parameters used for our experiments: 1) Energy of electrons pc = 30 MeV 2) Repetition rate 13 MHz 3) Pulse width ~2 ps 4) “1 electron per bunch” mode. (U. Lehnert et al.), ~100 Hz Gate voltage 8.5 V mainly 1 electron per bunch Gate voltage 9.5 V 1-7 electrons per bunch Gate voltage ~6.5 V 1 electron per bunch Single electron mode. QDC spectra from plastic scintillator before MRPC unit to be tested.

5. Effective size of single e- beam Horizontal scan Vertical scan 1.2cm * 20 cm/ns → σbeamsize = 60 ps

6. 3 mm 2 σ 25 mm Cross-check: Time resolution of MRPC as a result of beam-spot size Time spectrum one side σraw = 4.3 ch → 108 ps Conclusion: Averaging of right and left side Is necessary to study “pure” time resolution (σraw2-σbeamsize2)1/2 = 90 ps After walk correction: σfinal = 95 ps

7. Raw timing spectrum Walk Charge [1 Ch =25 fC] Time [ 1 Ch=25 ps ] Correction Time [ 1 Ch=25 ps ] Prototype tests at ELBE (by FZD and GSI groups, every 2 months). Walk-Correction procedure • Analysis procedure • Efficiency • Definition of event: we register signal from both ends of a target strip (strip where e- beam shoots). • We consider two neighboring strips because of the beam size. • Efficiency = (Number of RPC events) / (Number of trigger events) • Time Resolution • Calculation of position independent time value T=(t1+t2)/2, where t1 and t2 – TDC data from opposing ends of strip, relative to accelerator RF signal. • Walk correction by second + first order polynomial. • Quadratic subtraction of electronic noise: σEL ~ 25 - 35 ps Timing spectrum after correction for time walk,  ~ 90 ps

8. One and the same strip read out on right+left side, main strip and crosstalk Right side:Main strip and crosstalk Left side:Main strip and crosstalk Charge [25 fC] Charge [25 fC] Time [25 ps] Time [25 ps] Charge [25 fC] Charge [25 fC]

9. Time resolution, efficiency and cross-talk, 2x3 gap prototype TDC spectrum before and after walk-correction σEXP = 111 ps QDC spectrum

10. Time resolution, efficiency and cross-talk, 2x2 gap prototype TDC spectrum before and after walk-correction σEXP = 102 ps QDC spectrum

11. Comparison of different front-end electronics (2x2 gap prototype) PADI 2 FOPI FEE1

12. Time resolution, efficiency and cross-talk (2x2 gap prototype) for different front-end electronics: FOPI, PADI & ALICE

13. Time resolution and efficiency (2x2 gap prototype) for different front-end cards: FOPI, PADI & ALICE

14. Time resolution and efficiency with and without transformers (1) Charge [25 fC] Charge [25 fC] Time [25 ps] Time [25 ps] Charge [25 fC] Charge [25 fC] With transformers Without transformers

15. Time resolution and efficiency with and without transformers (2)

16. Summary • Past and current activity • Efficiency for minimum-ionizing particles (experiments at ELBE) • Efficiency for 175 MeV quasi-monochromatic neutrons (experiment at TSL Uppsala) • Timing resolution of minimum-ionizing particles signals (experiments at ELBE) • Electrical and cosmic-ray measurements of detector performance. • Differential readout. Alice and PADI front-end cards • 2 x 2 = 4 gap structure seems to give satisfactory timing + MIP efficiency • Single-ended readout of central anode with FOPI FEE1 gives best results • Cross-talk level depends on interstrip spacing, ~10% level possible for ~1mm spacing • Impedance transformers don’t seem to significantly change the situation • Outlook • Continue ELBE tests • Development of “big” prototype, 2 x 0.5 m

17. MRPC prototype developed and built at FZD: stack of glass plates

18. Determine efficiency and time resolution of MRPC w/ electrons? • minimum-ionizing particles • MRPC operation can be studied independently from neutron conversion efficiency • time resolution is not dominated by reference detectors or reactions • caveat 1: low duty-cycle and high pile-up of conventional electron machines (DC or NC-RF) • caveat 2:convenient 103 e-/s correspond to a beam current of 1.6*10-16 A which is very hard to diagnose