MPGD’s Workshop at NIKHEF April 16th 2008

1. I3HP-JRA4 Parallel Ionization Multiplier (PIM) : a multi-stage device using micromeshes for tracking particles Parallel Ionization Multiplier (PIM) : a multi-stage device using micromeshes for tracking particles J. BEUCHER jerome.beucher@cea.fr Dominique THERS, Eric MORTEAU (SUBATECH, Nantes, France) Vincent LEPELTIER † (LAL, Orsay, France) MPGD’s Workshop at NIKHEF April 16th2008

2. Outline • Part 1 • PIM principle • MIP’s tracking performance • Part 2 • Ion feedback suppression • Conclusions

3. Drift electrode Micromesh 3 Micromesh 2 Micromesh 1 PIM « Parallel Ionization Multiplier » Framed mesh with 10x10 cm² active area Drift 10 cm 50 µm 3 mm Kapton spacer foil etched by YAG laser Clean room PIM is a two amplification stages gaseous device based on micromeshes.

4. Modular prototype • 1-Large choice of meshes: • Electroformed Nickel mesh • Chemically etched Copper mesh with pillars from Rui de Oliveira’s lab (CERN) 3- Modular mechanical structure (S. Lupone): (µm) Holes Thickness Bar Pitch Hold-down frame Spacer frame (PVC) Mesh frame (FR4) Kapton spacer foil (or pillars) 1 mm 60 µm - (e = 5µm, hpillars = 25 ou 50 µm) Øholes=30µm 2- Large choice of gap thicknesses : 25, or 50 µm  pillars of CERN meshes 50, 75,125 et 220 µm  Kapton foil

5. 55Fe X @ 5,9 keV Systematic studies

6. Electronic transparency (%) Electronic transparency (%) Electron transmission (1/2) Electronic transparency : Drift or transfer stages 500 LPI e- Standard electroformed mesh 500 LPI (125 µm) CERN mesh Amplification gap CERN mesh (50 µm) Electronic transparency depends on mesh geometry. Slight dependence has been observed with different gaseous mixture (minor effect) But full collection efficiency could be reach easily by appropriate field ratio

7. 200 LPI 670 LPI (PIM 50-125 µm) 500 LPI 1000 LPI Extraction efficiency Cext ET/EA2 Electron transmission (2/2) 50-125 µm Extraction efficiency : (670 LPI) 50-200 µm 50-220 µm Pre-amplification gap EA2 e- ET Extraction efficiency Cext Transfer stage ET/EA2 A good choice of mesh geometry, gap thickness and gaseous mixture allows to achieve high extraction efficiency Cext~ 25 % at operating conditions with 220 µm gap thickness and 670 LPI mesh

8. Total gain 3 mm, Ec =1 kV/cm Maximum gain : last point before spark induced by 5.9 keV Xrays 500 LPI A2 = 125 µm 670 LPI 3 mm, ET ~1 kV/cm CERN mesh A1 = 50 µm PIM 50-125 µm(CERN, 670LPI, 500LPI) anode PIM : Very high total gain could be achieved (few 105 with Ne+10%CO2 ) with low electric fields Total gain MM 50 µm MM 125 µm Energy resolution ~20% (FWHM)

9. PIM performances with hadrons

10. Discharge probability measurement setup • High hadron flux p/p+ : • 10 GeV/c, few 105/spill (T9) PS @ CERN • 150 GeV/c,6.107/spill (H6) SPS @ CERN Beam p+ @ 10 or 150 GeV/c Prototypes Beam counter Plastic scintillators + Photomultiplier for beam profile monitoring and alignment

11. 125 µm A2 3 mm A1 50 µm Discharge probability PIM « Standard » PIM : extraction efficiency optimized Discharges probability [hadron-1] 200 µm A2 3 mm A1 50 µm Total gain Discharge probability lower than 10-9 per incident hadron at G~5000 with PIM

12. PIM_01 PIM_02 Prototypes for spatial resolution measurement • 2 prototypes back to back • Low material budget • Segmented anode : 512 strips (width=150 µm, pitch=195 µm) • 1024 GASSIPLEX channels Honey comb (5mm) Front-end (GASSIPLEX +12 bits ADC) • Active area 10x10 cm² Removable 55Fe source to simple gain monitoring

13. Efficiency [%] GA2 ~ 100 GA2 ~ 200 95 % Total gain Spatial resolution PIM 50-125 P1 Beam (<104/spill) P2 p+,p PIM_1 PIM_0 Spatial resolution (for one plane) Spatial resolution x~51 µm at the beginning of efficiency plateau (G~5000) GA2 ~ 100 GA2 ~ 200

14. Ion Feedback Suppression

15. Ion Feedback Filtering (PIM 50-125) V. Lepeltier 90Sr (~1 MeV) intense source Second ion filtering pA Idrift , Iprimary 3 mm No ion filtering expected because mostly field lines in transfer space are focused inside pre-amplification gap 500 lpi 125 µm 500 lpi 3 mm CERN mesh 50 µm anode pA Ianode First intrinsic ion filtering Current measured by KEITHLEY picoammeter Fractional Ion Feedback N.B : No mesh alignment (random arrangement)

16. Fractional Ion Feedback B=0T

17. Conclusion • Modular prototype and systematic studies allowed us to optimize geometry to reduce discharge rate induced by high hadron fluxPdisch ~ 10-10 hadron-1 (@ G~5000) • A multi-stage device using micromeshes with only two amplification stages have very promising performance for tracking particles under high rate conditions. • Preliminary results with PIM show good properties to avoid ion feedback without using DC ion gate FIF below 10-4 could be easily achieved with appropriate meshes • Complementary tests with high magnetic field are needed • Technology investigation is required to scale uptowardslarge area

18. Back-up

19. MICROMEGAS (MICRO-MEsh GAseous Structure) 50 µm Ø=39µm Grille 500 LPI nickel (e = 3 à 6 µm) • Ionisation primaire • Dérive des charges primaires • Passage de la microgrille pour les e- • Multiplication : avalanche électronique • Induction du signal

20. Charge spreading Cosmics 50 µm + 3 mm transfert stage Cluster multiplicity X 1.5 Large transfert thickness gap  could be used to spread charge cloud

21. Back-up Gain VS Et Cext augmente Te diminue Te diminue plus vite que Cext n’augmente Cext augmente Te ~ 100 %

22. Back-up Cext VS gaz

23. Caractérisation de l’électronique (1/3) Mesures des piédestaux et du bruit : <sigma> ~ 1,4 canaux ADC <Piédestaux> ~ 1170 canaux ADC Réponse homogène de l’ensemble de la chaîne électronique d’acquisition Bruit moyen ~ 1200 e- Seuil d’acquisition @ 5 ~ 6000 e-

24. Back-up

25. Etiquetage des décharges Typiquement 1V Décharge « vue » à travers une capacité Objectif : Mesurer Pdech en fonction du gain Véto (qq secondes)  Nécessité de s’affranchir du gain variable après 1 décharge

26. Back-up GEM + MICROMEGAS Drift GEM µ-grille

27. Back-up Influence du champ de transfert (Et) Augmentation de Et = extraction plus importante  Diminution de Pdech pour un gain donné

28. Mesures préliminaires Probabilités de décharge avec un détecteur MICROMEGAS : p+/p @ 10 GeV/c (ligne T9 PS) 1- Reproductibilité des résultats MICROMEGAS (125 µm) PS et SPS 2- Caractérisation de la probabilité de décharge pour différents gaps d’amplification • GA1 > 1000 • Pdech dépend fortement de la hauteur avec le gap • GA1 < 1000 • Pdech quasi-indépendante du gap Gain total

29. Pdech @ G =4000 GA2 ~ 4000 GA2 ~ 2000 MICROMEGAS 125µm GA2 ~ 4000 GA2 ~ 200 GA2 ~ 200 Gain total Pdech @ G=2000 Gain total GA2 ~ GA1 MICROMEGAS 125 µm MICROMEGAS 125 µm MICROMEGAS 125 µm Gain total Gain total Influence de GA2 (pré-amplification) Probabilités de décharge avec un détecteur PIM 125-125 µm : 125 µm A2 A1 125 µm GA2 ~ 4000 Gain total  Minimiser le gain dans chaque étage d’amplification

30. 125 µm 50 µm A2 A2 1 et 3 mm 3 et 6 mm A1 A1 125 µm 50 µm Influence du gap de transfert Indépendant de la hauteur de l’espace de transfert

31. 125 µm 125 µm A2 A2 3 mm 3 mm A1 A1 50 µm 125 µm GA2~200 GA2~200 Influence du gap d’amplification (A1) Gap de 50 µm au contact de l’anode Collection rapide des ions Minimisation de Pcorr