1. TIDE TESTS AT GDD LAB M. Casiraghi and F. Vasi

2. New detector configuration Low pressure chamber anode

3. Acrylic board with 5 holes Collimated surface barrier detector for counting primary particles Source collimator Internal side External side Semiconductive cathode Plate of 8 mm thickness 5 holes of 1.5 mm diameter 6 mm pitch

4. Test of acrylic plate (Propane) Measurements with Am241 source: correlation of the hole signal with the alpha signal Signal from surface barrier detector (primary particle) Signal from the holes (ions) Signal from the holes enlarged view In propane at 2 mBar, HV 2kV signal amplitude ~ 50 mV

5. Measurements at PTB microbeam Protons: 3 MeV, 10 MeV Alphas: 5 MeV, 8 MeV, 20 MeV Beam size: 3 um at vacuum window Adjustable frequency from ~ 10 Hz Next beam time end of October

6. Efficiency vs primary frequency (alphas) Ions/alpha expected in the volume at 3 mBar 20 MeV: ~100 8Mev ~ 200 (not including beam and detector geometry) __ mean counts/trigger --- counts/trigger (only trigger with signal) __ % of empty triggers (triggers with no signal) % of empty triggers

7. Goals of the tests Improvement of ion detection efficiency Long dead time: -cathode recharge time test of cathode materials - Dupont kapton XC: uncontrolled discharges (more layers?) - A. Breskin RPWELL materials -charge-up of hole walls glass GEM – Y. Mitsuya: OK for thick structure (1cm T, 1mm D) -dark rate gas impurities (water scintillation, photo-effect) - PEEK, glass field emission - cathode material Low probability for ion-impact ionization: - thicker boards - compare efficiency with different LET radiation (p, alpha, different energies @ PTB) PEG3PEG3C Ohm·cm8.5 × 10 12 4.5 × 10 14

8. Additional tests Test different gasses -Ar -ArCO 2 -Ar-methane Test different board thicknesses Acrylic of 10 mm, 8 mm, 6 mm - measure of efficiency (counts/primary) and dark rate Measure the signal amplitude as a function of the applied HV. to study the signal generation mode

9. PEEK plate

10. Tests with Argon - 2.5 mBar Acquisition gate Hole signal Alpha signal + scintillation ?

11. Tests with Argon – 3.5 mBar Lower peak at higher pressure Hole signal has smaller amplitude than in propane

12. 4 mbar 6.5 mbar Test with Argon with previous detector

13. Preliminary measurements – 3.5 mBar E/P [V/cm/mBar]dark rate [Hz]SNRcounts/trigger 71439.201.770.19 89345.901.930.18 107163.502.000.27 125075.001.850.19 E/P [V/cm/mBar]dark rate [Hz]SNRcounts/trigger 4645.933.860.18 81146.220.36 93661.171.130.25 1071117.781.040.30 Argon Propane

14. Simulations Argon Propane

15. Back-up slides

16. Purpose: Development of a device for characterization of radiation track structure for study of radiation biological effectiveness Simple damage REPARABLE Complex damage IRREPARABLE 50 base pairs ~ 16 nm ~ 2 nm Evidences that the local clustering of energy transfer points, in particular ionizations, is important for the production of initial damage to cells MC simulations show high LET radiation induced large ionization clusters are responsible for complex DNA damage. Experimental characterization for benchmarking MC simulations and characterize mixed or unknown fields Ideal detector would provide information on spatial distribution of ionization events with single ionization resolution in nanometric volumes of biological tissue (water)

17. The track imaging detector Anode providing drift voltage EdEd EaEa RTGEM-like detector, 2D array of ion counters Sensitive volume: low pressure propane gas 1-5 mbar ~100s nm track length in water Cathode providing accelerating voltage Secondary electron avalanche moving towards the PCB surface Primary ion producing ion impact ionization Readout strips X y hit Bashkirov, V. A., Hurley, R. F., Schulte, R. W. A novel detector for 2D ion detection in low-pressure gas and its applications. NSS/MIC Conference Record, IEEE, 694-698, 2009

18. Experimental set-up at LLU

19. Prototype characterization – Detector signal Detector signal on 50 Ω load Diode signal Pulse of 5mV and 400 ns gain of ~10 8 Source: Am241 alphas 2mm beam Working gas: propane PCB: 3.3 mm G10 board with common top electrode (gold plated) Holes 0.8mm, pitch 2mm Cathodes: high resistivity glass semi-conductive glass P = 4 mbar HV = -800 V E d = 10 V/cm

20. Semiconductor glass Mean counts/trigger = 18 High resistivity glass Mean counts/trigger = 14 ● beam Ø= 2 mm ● propane at P= 4 mbar ● E d and E a neglected Semiconductive glass ● Different distribution shape, peak shifted to larger counts number ● Smaller number of empty triggers ● Shorter recharge time ● Still signal disappears below 2 mbar ● Still low number of detected ions G4 simulations of  g Including geometrical efficiency ideal Including geometrical efficiency ideal Ionizations/alpha

21. Measurements results: Measure of efficiency with 3 detector versions varying gas pressure and accelerating field intensity Ion impact probability ÷ E/P percentage of primaries producing at least one ionization in one of the holes Efficiency vs plate thickness 2/2

22. Measurements results: Measure of efficiency with 3 detector versions varying gas pressure and accelerating field intensity Ion impact probability ÷ E/P percentage of primaries producing at least one ionization in one of the holes Efficiency vs plate thickness 2/2

23. Measurements results: Measure of efficiency with 3 detector versions varying gas pressure and accelerating field intensity Ion impact probability ÷ E/P percentage of primaries producing at least one ionization in one of the holes

24. Chamber (Aluminum+plastic lid) Swagelok fitting MKS Baratron 626 Control valve MKS 248A Swagelok fitting Swagelok tee Fast evacuation valve Needle control valve Propane cylinder Working pressure: 1-3 mbar propane, continuous flow Chamber internal dimensions: 20 x 10 x 7.5 cm^3 Flow for normal operation controlled by metering valve swagelok SS-SS4 0.004 Cv max flow ~ 1-4 std cc/min Evacuation before injecting propane (minimum P = 0.05 mbar). Fast evacuation valve (Diaphragm valve swagelok SS-DSS4 0.3 Cv) Tubing stainless steal ¼'' Pump Pressure controller MKS 250 Gas System Hole signal