Design and Construction of a TPC using GEM Foils for Gas Amplification

Transcription

1 esign and onstruction of a TP using GM Foils for Gas mplification Martin Killenberg Sabine latt Manuel Giffels Gordon Kaußen Sven Lotze Joachim Mnich strid Münnich Stefan Roth drian Vogel Michael Weber III. Physikalisches Institut I Nuclear Science Symposium Rome, October 24 Martin Killenberg esign and onstruction of a TP 1

2 Overview Measurement of harge Width aused by a Triple-GM Structure ependency on Magnetic Field Ion ackdrift Parametrisation of harge Transfer Minimisation Track istortions TP Prototype esign of the Fieldcage Readout lectronics Martin Killenberg esign and onstruction of a TP 2

3 harge Width: Measurement Test chamber, 55 Fe source node strips, 3 m pitch 5 1 luster Width [µm] harge [ counts] luster enter [Streifen] node strips ata points for 3 events Spatial charge distribution Martin Killenberg esign and onstruction of a TP 3

4 harge Width: ependency on -Field Magboltz simulation Measurements - / -field dependency (caused by diffusion): harge width [µm] Magnetic field [T] Measured with 5 T magnet at SY MGOLTZ simulation takes different electric fields in GM structure into account. Transverse diffusion is overrated by the used MGOLTZ version. harge broadening is dominated by diffusion. Martin Killenberg esign and onstruction of a TP 4

5 Ion ackdrift: Setup and Parameters I K n athode harge transfer determined by 7 chamber parameters d = 4 mm (3 GM voltages, 4 fields) I G1K I G1 n n U GM 1 Parametrisation of d T1 = 2 mm T1 transfer coefficients I G2K n I G2 I G3K I G3 n n n d T2 = 2 mm U GM 2 T2 U GM 3 alculation of ion backdrift ( effective gain ( ) and ) d Ind = 2 mm Ind I n node Optimisation for minimal ion backdrift Martin Killenberg esign and onstruction of a TP 5

6 Ion ackdrift: Finding Minimum xample: Minimal ion backdrift is achieved for lowest.35.3 Minimal Ion ackdrift Measurement Prediction from Parametrisation trans2 [V/cm] Martin Killenberg esign and onstruction of a TP 6

7 ! (' ( Ion ackdrift: Optimisation athode Minimal ion backdrift can be achieved with: GM 1 GM 2 GM 3 node/ Pickup rift T1 T2 Ind ' &% "$#..... fixed at 24 V/cm.... small influence maximal &% "$#.... small influence minimal ) &% "$# * ' &% "+#.... maximal maximal and &% "+# allow variation of effective gain without changing. Martin Killenberg esign and onstruction of a TP 7

8 1 Ion ackdrift: Latest Results Relative ion backdrift [ ] Q I = 1 Q primary Prediction from parametrisation: independent of Lower, yields lower backdrifting charge For - *. : /, *. Q I = 5. Q primary ffective gain Q I = 2.5 Q primary Q I = 1. Q primary = 4 T, measured at SY Still an open question: How much ion backdrift can be tolerated Martin Killenberg esign and onstruction of a TP 8

9 Ion ackdrift: Track Measurements athode Shielding ackdrifting ions 55Fe source node/ Readout GMs 1m Large TP (1 m3 ) with triple-gm readout 55 Fe source fixed on cathode ontinuous intense ionisation Formation of ion tube between readout and source Martin Killenberg esign and onstruction of a TP 9

10 Ion ackdrift: Track istortions large ion backdrift small ion backdrift Martin Killenberg esign and onstruction of a TP 1

11 : : TP Prototype: onstruction 5T Magnet at SY 26 mm chamber diameter SM resistors as voltage divider pitch = 2.8 mm GM readout from test TP is used drift distance = 26 cm maximum drift field = 1 ; <= materials with low density Martin Killenberg esign and onstruction of a TP 11

12 TP Prototype: Radiation Length poxy Resin 4 x.125 mm Kapton GFK,.25 mm l Foil,.5 mm 2.8 mm Pitch u Strips,.3 mm, ramid Honeycomb, 5 mm Fraction of Radiation Length Glass Fibre.23 % l Foil.6 % Kapton.2 % u Strips.29 % poxy Resin.14 % Honeycomb.6 % Total 1% of a radiation length : 3 % of a radiation length possible (TSL TR) Martin Killenberg esign and onstruction of a TP 12

13 F TP Prototype: First Results First vent Homogeneous rift Velocity rift Time [ µs] Position z [cm] Martin Killenberg esign and onstruction of a TP 13

14 TP Prototype: Readout lectronics Goal: evelop a test readout with 512 channels for our TP Requirements: Fast preamplifiers to study time resolution Small preamplifiers to allow compact design Fast s Preamplifier ata aquisition 3 25 urrent Status: First signals with preamplifiers counts G No full instrumentation yet ata time [ns] Test chamber pulse Martin Killenberg esign and onstruction of a TP 14

15 H / Summary harge broadening is dominated by diffusion between GMs. Influences of voltages and fields in a triple-gm structure are well understood and can be optimised. Moderate effective gains allow - * istortions of observed tracks depend on ion backdrift. TP prototype for use in magnet constructed. evelopment of new readout electronics for use in test beam ongoing. Martin Killenberg esign and onstruction of a TP 15