RESIST - 03 Nov 2008 P. Colas 1 RESIST Etat des lieux, bulk résistif, techniques disponibles

RESIST - 03 Nov 2008P. Colas2 Introduction : buts Améliorer la résolution par un meilleur partage de charge Améliorer la résolution par un meilleur partage de charge Protéger le détecteur et lélectronique contre les étincelles Protéger le détecteur et lélectronique contre les étincelles Ceci est nécessaire pour obtenir la résolution voulue pour la TPC de lILC (100 microns) sans multiplier le nombre de canaux, et ceci peut être utile également pour T2K, si des problèmes de stabilité apparaissaient ou si une résolution meilleure que 500 microns savérait utile.

RESIST - 03 Nov 2008P. Colas3 Théorie analytique de la résolution Avec nos collègues japonais, nous avons mis au point une théorie analytique de la résolution: Effets de fluctuation dionisation, de fluctuation du gain, et de taille finie des pads, limitent la résolution. En raison du manque de partage de la charge entre pads voisins la résolution est, au mieux, de 10% de la largeur des pads 1/12 1/(12.N eff )

RESIST - 03 Nov 2008P. Colas4 Extrapolation à la TPC de lILC Conclusion: même avec un pas de 1mm, Micromegas avec des pads standard ne permettrait pas datteindre le but de 130 m de résolution. Cependant avec une feuille résisitive et des pads de 2.3 mm, ce but est largement atteint(courbe rouge).

RESIST - 03 Nov 2008P. Colas5 Feuille résistive Une feuille résistive collée sur le plan danode en fait un réseau de résistances et capacités qui étale la charge Une feuille résistive collée sur le plan danode en fait un réseau de résistances et capacités qui étale la charge Proc. of LCWS 2005 On obtient une résolution de 50 microns à petite dérive (et à toute dérive pour B assez grand) Faisceau test à KEK B=1T Micromegas avec feuille résistive Q ns Cosmiques en champ magnétique Dapnia 07-36, soumis à NIM A

RESIST - 03 Nov 2008P. Colas6 Bulk résisitif La technologie bulk NIM A 560 (2006) 405 permet une grande robustesse et labsence de zones mortes (pas de cadre) La technologie bulk NIM A 560 (2006) 405 permet une grande robustesse et labsence de zones mortes (pas de cadre) Idée: la combiner à la technologie du résistif Idée: la combiner à la technologie du résistif RESIST : 12 personnes+1 postdoc+ST RESIST : 12 personnes+1 postdoc+ST Tests en labo: bulk résistif, mesures de résistivité, uniformité, etc… Nouveau labo opérationnel mi-novembre Tests en labo: bulk résistif, mesures de résistivité, uniformité, etc… Nouveau labo opérationnel mi-novembre Tests en faisceau ou cosmique au CERN et/ou TRIUMF ou Fermilab et à DESY. Tests en faisceau ou cosmique au CERN et/ou TRIUMF ou Fermilab et à DESY.

RESIST - 03 Nov 2008P. Colas7 TECHNIQUES Film Sheldhal- AlSi cermet + colle flobond + procédé drytac (Carleton) Film Sheldhal- AlSi cermet + colle flobond + procédé drytac (Carleton) Pâte résistive (CERN, Rui de Oliveira) Pâte résistive (CERN, Rui de Oliveira) Couche déposée (ASiH, AsiP) (MIT unine, Nicolas Wyrsch) Couche déposée (ASiH, AsiP) (MIT unine, Nicolas Wyrsch)

RESIST - 03 Nov 2008P. Colas8 Several techniques are being tested for the resistive coating 1)Carbon-loaded kapton. An old technique first tested in Carleton, using a Dupont film 3 MOhm/sq. Improvements on application of the resistive foil and switch to bulk. First results promising. One panel recently produced.

RESIST - 03 Nov 2008P. Colas9 2) Prepreg+ screen printing This has been tried at CERN. 2 prototypes of 10x10 cm (2 and 8 MOhm/sq) have been tried at Saclay. There is not clear evidence that they are spark protected. Even one of the detector has been damaged by the HV during the test. Still such a layer will be applied to a CERN panel.

RESIST - 03 Nov 2008P. Colas10 Plasma deposition of thin layers (N. Wyrsch, Neuchatel, used for SiProt) Preliminary tests going on. Next step: make a small bulk 12x14 cm 2 with 2 layers of different resistivity, and then cover a PCB with pads and make a bulk out of it

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RESIST - 03 Nov 2008P. Colas12 In-situ TEST at DESY Gas-box Trigger counters

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RESIST - 03 Nov 2008P. Colas15 New detector with resistive foil in the gas box

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RESIST - 03 Nov 2008P. Colas18 La TPC du Large Prototype est presque prête pour prendre des données

RESIST - 03 Nov 2008P. Colas19 Took data with P5 gas with standard pads on October 2 and 3 at 50 MHz sampling rate, and 200ns peaking time. Took data with P5 gas with standard pads on October 2 and 3 at 50 MHz sampling rate, and 200ns peaking time. Tested the whole chain again on October 27, and switched to the new module (with C-loaded kapton resistive foil) in the test box (took about 2 hours) Tested the whole chain again on October 27, and switched to the new module (with C-loaded kapton resistive foil) in the test box (took about 2 hours) Took data since October 27 with P5 Took data since October 27 with P5 50 MHz sampling rate, 200 ns peaking time 50 MHz sampling rate, 200 ns peaking time 100 MHz sampling rate, 200 ns peaking time 100 MHz sampling rate, 200 ns peaking time 50 MHz sampling rate, 400 ns peaking time 50 MHz sampling rate, 400 ns peaking time Switched then to T2K gas (Ar/CF4/isobutane:95:3:2) Switched then to T2K gas (Ar/CF4/isobutane:95:3:2)

RESIST - 03 Nov 2008P. Colas20 plans Take beam data in the magnet in the period of weeks (+1 or 2?) - Install and commission beam trigger (today) - Mount standard panel + 6 dummies on the endplate - Finalize and connect cathode - Cool down magnet - See how to set HV (1st ring to V) - Order gas : 25 bar per bottle, 1 bottle for 18 hours at 60 l/h, 1 bottle in 55 hours at 20 l/h. - Add bubbler - Excite magnet on November 10 - Then start beam data taking and analysis - switch to resistive anode week 47

RESIST - 03 Nov 2008P. Colas21 Simulating and understanding SiProt A single spark kills a TimePix chip A single spark kills a TimePix chip High current, hot plasma -> destroys circuit High current, hot plasma -> destroys circuit A sufficiently thick SiProt layer reduces and softens the sparks A sufficiently thick SiProt layer reduces and softens the sparks How protection works? How protection works? Allows charge to stay over the pad, lowering the local potential Allows charge to stay over the pad, lowering the local potential Limits the current thru the amplifier Limits the current thru the amplifier Protects mechanically Protects mechanically Avoids points, softens the surface? Avoids points, softens the surface? Any damage to the signal? Any damage to the signal? Amplitude loss? Amplitude loss? Charge sharing with neighbouring pads? Charge sharing with neighbouring pads? Short-circuit of the amplifiers Short-circuit of the amplifiers Introduces dead time? Introduces dead time? TO ANSWER, NEED A SIMULATION

RESIST - 03 Nov 2008P. Colas22 Orders of magnitude R neighbour R thru e l L R neighb = L/el = /e for square pads For 10 µ aSi, =10 11.cm, R=10 14 /square R thru = e/Ll ~ R neighb /R thru = L 2 /e 2 e<<L to avoid spreading the charge by side conductivity. The charge preferentially escapes thru the pad, but with an extremely high resistance. C neighb = r Le/l = r /e for square pads C thru = r Ll/e (note r ~11 for Si) The influence acts preferentially thru the pad if L>>e

RESIST - 03 Nov 2008P. Colas23 R neighbour R thru e l L Also R thru >> 1/C to leave the induced signal (OK with cm within 3 orders of magnitude for 10 ns signals) Equivalently, RC time constant >> 10ns The signal is fully capacitive 1/C thru 1/C neighbour

RESIST - 03 Nov 2008 P. Colas 24 5 pixels gas Siprot 25 Pads 25 TimePix Preamps gas: 10x10x10 elements/pad SiProt: 10x10x10 elements/pad « central » gas element. C network (special ones fo edges) « central » SiProt element RC network (special ones fo edges) Pads:Metallisation of the last SiProt elements « Full » shape 100% of pixel aluminized « Cross » shape 12% of pixel Al, rest SiN 2 Charge Injection at the gas / SiProt interface in the central pixel Size = 4 elts 3 positions. Top= HT (ac grounded) SiProt Simulation with Analog Artist E. Delagnes, S.Turnbull

RESIST - 03 Nov 2008P. Colas25 Note that SiProt is very different from the charge spreading for improving the resolution (M. Dixit et al.). In that case, there is an insulating layer ( µ) below a low-resistivity coating: 1 M /sq, 100 nm (i.e. 10.cm). In that case, the charge obeys the telegraph equation (see Stephen Turnbulls talk). In SiProt, the signal is capacitive and the charge slowly evacuates in thru the coating and the amplifier. This Analog Artist simulation can also be used for double layers with 2 different resistivities. Run time for SiProt: 10 h per set of parameters. 25 AFTER Preamps gas resistive insulator

RESIST - 03 Nov 2008P. Colas26 Signal development Charge pulse: 1ns trapezoidal current pulse Injection in the middle Injection in the corner Injection in between

RESIST - 03 Nov 2008P. Colas27 Results Pads fully covered with Al

RESIST - 03 Nov 2008P. Colas28 Results Pads 12% covered.

RESIST - 03 Nov 2008P. Colas29 thickness Signal frac. on central pad (Full pads) Signal frac. on central pad (cross) 10 µ 94 % 76 % 15 µ 83 % 57 % 20 µ 70 % 44 % Charge injected in the middle of the pad

RESIST - 03 Nov 2008P. Colas30 Pad Response Function

RESIST - 03 Nov 2008P. Colas31 The first resistive bulk works to perfection. The first cosmics seen show a charge spreading as expected