T 2 GEM Production in Helsinki Kari Kurvinen

T 2 GEM Production in Helsinki Kari Kurvinen 31. 1. 2006 TOTEM T 2 EDR meeting Radiation Detector Laboratory of Helsinki Institute of Physics (HIP) and Department of Physical Sciences of University of Helsinki.

T 2 GEM design 28 cm • triple GEM foils • Ar/CO 2 70/30 gas mixture • operating gas gain M = 8000 HV resistor divider board • design by F. Sauli & L. Ropelewski based on COMPASS GEM design • GEM foils manufactured by CERN • readout boards by CERN and a commercial company Test Cards No bonding anymore

READOUT STRUCTURE fully digital readout (no analog information used) 512 strips (pitch of 400 microns) 1560 pads (2 x 2 -> 7 x 7 mm 2) readout via connectors VF AT A PV XXX support rails radial strip readout split asymmetric spacers HV

T 2 GEM production in Helsinki • construction of 40+ GEM detectors for TOTEM T 2 is on responsibility of the Helsinki group. • a ”GEM production line” has been constructed in the detector laboratory of HIP • Compass GEM production as a guideline (ref. M. Capean, B. Ketzer, A. Placci, L. Ropelewski, F. Sauli, M. van Stenis; Construction of GEM Detectors for the Compass Experiment, Technical Note TA 1/00 -03, CERNEP/TA 1).

Facilities for large GEM production oven for large foils ultrasonic bath for large frames dryboxes for leakage current measurements and for storage large area probe station

Production in clean rooms • almost all the manufacturing phases in clean rooms. • >120 m 2 clean room (classes 100 & 1000) available. • usage currently shared by TOTEM and ALICE groups.

Clean room monitoring Particles • temperature and humidity is continuously recorded as well

Main tasks in the production I. cleaning and varnishing of the frames. II. glueing of the drift electrode. III. streching and glueing of the GEM foils. IV. testing the readout boards. V. assembling all the parts together. VI. assembling connectors (gas, HV). VII. checking gas tightness. VIII. electronic tests. • Handling procedures of the separate detector components are registered into a database.

A lo o t a m f a u n o w l ! k r

• visual inspection (coordinates of the major defects recorded). • optical scanning • dried in a desiccator. • 1. leakage current measurements of all the segments in the foils (criteria <0. 5 n. A). • streching and glueing on the frames • curing > 16 hours in oven • cut out from the foil • 2. leakage current measurements GEM FOILS

Leakage current measurements of GEM foils • the four segments of the GEM foils are measured separately by a picoamp meter. • leakage currents measured three times during assembly (as a bare foil, after framing and after gluing into a stack). 36 measurement / detector • a foil approved if current stays < 0. 5 n. A for 30+ min @500 V HV ramp up in N 2 > 5 min in N 2 C-segment spark! 12 min B-segment Present status: 21 foils checked (incl. prototypes), 2 failed 12 min

READOUT BOARD • • visual inspection capacitance measurement A. B. probe station & LCR meter semiautomatic relay system connectors soldered short circuits burned

Assembling components together • • • in clean room of class 100 all the three framed GEM foils are glued one after the other on the drift frame (a special press constructed). consumption of the glue measured. 3. leakage current of the GEM foils checked after gluing. GEM stack glued on the readout board.

Assembling connectors gas tightness by Araldite & Dow Corning 1 -2577 assembling: i. the voltage divider PCB ii. the adapters for the gas connectors and blocking the holes on the backside. iii. HV cables

TESTS • • GAS LEAKAGE TEST ELECTRONIC TESTS a. HV test in CO 2 or N 2 b. Basic measurement (gas amplification, energy resolution) c. Stability measurement d. Gas gain scan over active area.

Gas tightness TOOLS AVAILABLE • comparison of inand outflow • leak detector • oxygen measurement from the outflow

Basic measurements of HG 1 55 Fe

Gas gain scan of readout sectors The gas gain of the whole readout sectors (128 strips or 120 pads) are measured. Due to different capacitances of pad and strip sectors and a limitation of preamplifier used the measurement may not be compared between pad and strip sectors.

Gas gain scan with a point source • • Different areas of the second half of the HG 1 GEM were irradiated by 55 Fe source (50 points) 128 strips or 120 pads readout Std. dev. : on inner strips on outer strips on pads 8. 1% 5. 8% 10%

STATUS Jan. 2006 Prototypes T 2 GEMs one for the beam test (Nov. 2004) two built in Helsinki during 2005 • two built in Helsinki during 2005 • chambers for 3 rd, 4 th and 5 th GEMs finished

Conclusions • the radiation detector laboratory of Helsinki has unique facilities to assemble and test large area gaseous detectors. • a production of TOTEM T 2 GEMs has successfully started.