1. Parallel Ionization Multiplier (PIM) : a multi-stage device using micromeshes for tracking particles MPGD’s Workshop at NIKHEF April 16th2008 April 16th 2008 Dominique THERS, Eric MORTEAU (SUBATECH, Nantes, France) Vincent LEPELTIER † (LAL, Orsay, France) J. BEUCHER jerome.beucher@cea.fr I3HP-JRA4

2. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 2 Outline Part 1 –PIM principle –MIP’s tracking performance Part 2 –Ion feedback suppression Conclusions

3. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 3 Drift electrode Micromesh 3 Micromesh 2 Micromesh 1 PIM « Parallel Ionization Multiplier » 10 cm PIM is a two amplification stages gaseous device based on micromeshes. Kapton spacer foil etched by YAG laser Clean room 50 µm 3 mm Framed mesh with 10x10 cm² active area Drift

4. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 4 1- Large choice of meshes:  Electroformed Nickel mesh  Chemically etched Copper mesh with pillars from Rui de Oliveira ’s lab (CERN) Modular prototype (e = 5µm, h pillars = 25 ou 50 µm) 1 mm - 60 µm Ø holes =30µm 2- Large choice of gap thicknesses : 25, or 50 µm  pillars of CERN meshes 50, 75,125 et 220 µm  Kapton foil 3- M odular mechanical structure (S. Lupone) : Holes Bar Pitch Thickness (µm) Hold-down frame Spacer frame (PVC) Mesh frame (FR4) Kapton spacer foil (or pillars)

5. 5 MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 55 Fe X @ 5,9 keV Systematic studies

6. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 6 Electron transmission (1/2) 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 e-e-e-e- Amplification gap Drift or transfer stages Electronic transparency (%) Electronic transparency : Standard electroformed mesh 500 LPI (125 µm) CERN mesh (50 µm) CERN mesh 500 LPI

7. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 7 200 LPI 500 LPI 1000 LPI 670 LPI E T /E A2 Extraction efficiency C ext (PIM 50-125 µm) E T /E A2 50-125 µm 50-200 µm 50-220 µm (670 LPI) Extraction efficiency C ext Electron transmission (2/2) e-e-e-e- Transfer stage Pre-amplification gap A good choice of mesh geometry, gap thickness and gaseous mixture allows to achieve high extraction efficiency C ext ~ 25 % at operating conditions with 220 µm gap thickness and 670 LPI mesh Extraction efficiency : ETET E A2

8. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 8 Total gain PIM 50-125 µm (CERN, 670LPI, 500LPI) A1 = 50 µm A2 = 125 µm MM 50 µm MM 125 µm 3 mm, E T ~1 kV/cm 3 mm, E c =1 kV/cm anode Maximum gain : last point before spark induced by 5.9 keV Xrays PIM : Very high total gain could be achieved (few 10 5 with Ne+10%CO 2 ) with low electric fields Energy resolution ~20% (FWHM) Total gain CERN mesh 670 LPI 500 LPI

9. 9 MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher PIM performances with hadrons

10. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 10 Discharge probability measurement setup Beam Plastic scintillators + Photomultiplier for beam profile monitoring and alignment Prototypes Beam counter   @ 10 or 150 GeV/c High hadron flux p/  + : 10 GeV/c, few 10 5 /spill (T9) PS @ CERN 150 GeV/c, 6.10 7 /spill (H6) SPS @ CERN

11. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 11 Discharge probability Discharge probability lower than 10 -9 per incident hadron at G~5000 with PIM 125 µm 50 µm A1 A2 3 mm Discharges probability [hadron -1 ] Total gain 200 µm 50 µm A1 A2 3 mm PIM « Standard » PIM : extraction efficiency optimized

12. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 12 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 PIM_01 PIM_02 Active area 10x10 cm² Honey comb (5mm) Front-end (GASSIPLEX +12 bits ADC) Removable 55 Fe source to simple gain monitoring

13. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 13 95 % G A2 ~ 100 G A2 ~ 200 Total gain Efficiency [%] Spatial resolution PIM 50-125 Spatial resolution (for one plane)  x ~51 µm at the beginning of efficiency plateau (G~5000)  +,p Beam (<10 4 /spill) P1 P2 PIM_0 G A2 ~ 100 G A2 ~ 200 Spatial resolution PIM_1

14. 14 MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher Ion Feedback Suppression

15. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 15 Ion Feedback Filtering (PIM 50-125) 3 mm anode pA 500 lpi CERN mesh 500 lpi 90 Sr (  ~1 MeV) intense source pA I anode I drift, I primary No ion filtering expected because mostly field lines in transfer space are focused inside pre-amplification gap First intrinsic ion filtering Second ion filtering N.B : No mesh alignment (random arrangement) Fractional Ion Feedback Current measured by KEITHLEY picoammeter 125 µm 50 µm V. Lepeltier

16. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 16 Fractional Ion Feedback B=0T

17. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 17  Modular prototype and systematic studies allowed us to optimize geometry to reduce discharge rate induced by high hadron flux P disch ~ 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. Conclusion  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 up towards large area

18. 18 MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher Back-up

19. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 19 MICROMEGAS (MICRO-MEsh GAseous Structure) Ionisation primaire Dérive des charges primaires Passage de la microgrille pour les e- Multiplication : avalanche électronique Induction du signal Grille 500 LPI nickel (e = 3 à 6 µm) 50 µm Ø=39µm

20. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 20 Charge spreading Large transfert thickness gap  could be used to spread charge cloud Cosmics Cluster multiplicity 50 µm X 1.5 + 3 mm transfert stage

21. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 21 Back-up Gain VS E t C ext augmente T e ~ 100 % C ext augmente T e diminue T e diminue plus vite que Cext n’augmente

22. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 22 Back-up Cext VS gaz

23. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 23 Caractérisation de l’électronique (1/3) Mesures des piédestaux et du bruit : ~ 1170 canaux ADC ~ 1,4 canaux ADC Réponse homogène de l’ensemble de la chaîne électronique d’acquisition Bruit moyen ~ 1200 e - Seuil d’acquisition @ 5  ~ 6000 e -

24. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 24 Back-up

25. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 25 Etiquetage des décharges Décharge « vue » à travers une capacité Typiquement 1V Objectif : Mesurer P dech en fonction du gain  Nécessité de s’affranchir du gain variable après 1 décharge Véto (qq secondes)

26. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 26 Back-up GEM + MICROMEGAS µ-grille GEM Drift

27. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 27 Back-up Influence du champ de transfert (E t ) Augmentation de E t = extraction plus importante  Diminution de P dech pour un gain donné

28. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 28 Mesures préliminaires Probabilités de décharge avec un détecteur MICROMEGAS :  G A1 > 1000 P dech dépend fortement de la hauteur avec le gap 1- Reproductibilité des résultats MICROMEGAS (125 µm) PS et SPS  G A1 < 1000 P dech quasi-indépendante du gap   /p @ 10 GeV/c (ligne T9 PS) 2- Caractérisation de la probabilité de décharge pour différents gaps d’amplification Gain total

29. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 29 Influence de G A2 (pré-amplification) Probabilités de décharge avec un détecteur PIM 125-125 µm :  Minimiser le gain dans chaque étage d’amplification 125 µm A1 A2 Gain total G A2 ~ 4000 MICROMEGAS 125 µm Gain total G A2 ~ 4000 G A2 ~ 2000 MICROMEGAS 125 µm P dech @ G =4000 P dech @ G=2000 Gain total G A2 ~ 200 MICROMEGAS 125 µm Gain total G A2 ~ G A1 G A2 ~ 200 MICROMEGAS 125 µm

30. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 30 Influence du gap de transfert Indépendant de la hauteur de l’espace de transfert 125 µm A1 A2 1 et 3 mm 50 µm A1 A2 3 et 6 mm

31. MPGD’s workshop, NIKHEF, April 16 th 2008 J. Beucher 31 Influence du gap d’amplification(A1) Gap de 50 µm au contact de l’anode Collection rapide des ions  Minimisation de P corr 125 µm 50 µm A1 A2 3 mm 125 µm A1 A2 3 mm G A2 ~200