Status of the TPG E.Radicioni MICE coll. Meeting - RAL, Oct. 2004

27/10/2004E.Radicioni2 Outline Recall of the main characteristics Construction and operation First of the detector behavior Design aspects –Electronics –Field-cage –Gas –Background

27/10/2004E.Radicioni3 The TPG is a cylindrical TPC equipped with GEM amplification and a special high-resolution pad-plane TPCs with GEMs are actively studied by several groups around the world in view of the linear collider experiments. The novelty of the TPG consists in the pad-plane, where projective readout promises high granularity with a reduced number of channels Dedicated design choices for MICE were –the dimensions (100cm length, 30cm diameter) to fit into the tracker magnet –The gas (He) chosen because of its low conversion probability

27/10/2004E.Radicioni4 Construction E B drift volume field cage GEM stage solenoid read-out plane

27/10/2004E.Radicioni5 The GEM foil Triple-layer structure Each layer divided in 8 regions, independently powered Max amplification depends on gas and HV. With good gas it can be as high as 10 6.\

27/10/2004E.Radicioni6 The hexaboard – ~ hexagonal pads size: 300  m pitch: 500  m – grouped into strips along 3 coordinates at 120 degrees (u, v, w) running at different depths

27/10/2004E.Radicioni7 Strips and pads

27/10/2004E.Radicioni8 300  m 500  m

27/10/2004E.Radicioni9 Spot the error … and correct it!

27/10/2004E.Radicioni10 Hexaboard quality, from this:

27/10/2004E.Radicioni11 … to this:

27/10/2004E.Radicioni12 Support structures  outer metal ring  o-rings for gas tightness  stiffener plate  GEMs support rings  guard ring

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27/10/2004E.Radicioni14 Assembling the detector

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27/10/2004E.Radicioni17 The dream team at work

27/10/2004E.Radicioni18 Last computations and timing checks …

27/10/2004E.Radicioni19... what is this detector trying to tell us ???

27/10/2004E.Radicioni20 55 Fe source calibration Absolute energy, equalization Preamp gain calibration is not included yet First indications are –Despite the lack of gain equalization, the energy resolution is already quite good –The plots are very sensitive to the cuts on cluster size, as expected from a properly working detector

27/10/2004E.Radicioni21 55 Fe source “beam profile” Unconnected strips Ill electronic channels –Dead –Noisy

27/10/2004E.Radicioni22 Capability of seeing detector structures 55 Fe source illuminates the center of the pad plane Large lines: spacer grid in between the GEMs: 2mm large Thin lines: non-working electronics channels

27/10/2004E.Radicioni23 55 Fe source All clusters ≥2 strips ≥3 strips

27/10/2004E.Radicioni24 U,V vs. W correlations out-of-line events are due to lack of gain calibration Correlation is important: it can be exploited as an additional tool for getting rid of fake combinations –In addition to the use of the 3 rd projection Compass is able to reject (almost all) fakes by this technique TPG COMPASS

27/10/2004E.Radicioni25 Low energy tracks 500 Ar/CO 2 90/10, 10cm/  s  total 50cm drift path e- from Sr source B=0.07T (1/10 nominal) Color code gives charge amplitude

27/10/2004E.Radicioni26 2 MeV/c electron in B=0.07T Transverse diffusion spreads the charge

27/10/2004E.Radicioni27 Intrinsic resolution 55 Fe X-ray conversion position can be determined by 2 projections, then cross-checked with the 3 rd one. The intrinsic resolution is VERY promising This has been obtained with a 3cm drift cell. Actual resolution over longer drift depends on gas properties.  ~40 µm U+V vs. W resolution

27/10/2004E.Radicioni28 Design improvements Electronics Ingredients for good resolution Gas choice Discussion on overall parameters A compact emittometer, alias TPG ?

27/10/2004E.Radicioni29 Electronics New electronics from ALICE Higher integration Total (including DAQ) 10 CHF / channel Digitization is close to detector (less noise) Data get out from the detector on a few optical fibers (elegant, simple) Large range of possible sampling frequencies up to 40 MHz.

3027 February 2004Luciano Musa / CERN - PH ALTRO EVOLUTION 4cards 16 ch 135 mm 1998 CHANNELS / CHIP: 1 POWER / CH: 120mW PRICE / CH: 50CHF Integrated ADCs 20 mm 4 PQFP SSOP mm 1999 CHANNELS / CHIP: 4 POWER / CH: 80mW PRICE / CH: 8CHF 2001 CHANNELS / CHIP: 1 POWER / CH: 16mW PRICE / CH: 5CHF

3127 February 2004Luciano Musa / CERN - PH Digital Conditioning of the TPC Signal EV 1 EV 2 EV 3 EV 1 EV 2 EV 3 EV 1 EV 2 EV 3 EV 1 EV 2 EV 3 ADC BC ITCFBC II

27/10/2004E.Radicioni32 Momentum resolution Position resolution is driven by –Readout pitch (fixed) –Diffusion in gas –Ionization and gain Gas choice is a key point: we should look for larger gain and ionization and smaller diffusions. Momentum resolution is driven by –Position resolution –Number of available points From the simple Glukstern formula: 50 points give dp/p resolution factor only 1.5 better than 20 points. If more distant points are affected by more diffusion, we should really consider limiting the number of points and the drift length.

27/10/2004E.Radicioni33 Gas choice

27/10/2004E.Radicioni34 Shorter field-cage? He/CO 2 1mNe/CO 2 18cm E500 V300 V Max HV50 KV5.4 KV Drift time 60  s6  s Drift velocity 1.68 cm/  m3 cm/  m Sampling freq2MHz10MHz Number of samples11860 Trans/long diffusion 1000/1600  m80/200  m Specific ionization10 e - /cm20 e - /cm Usable long. Slices11820 (shaper limited) N. Radiation lenghts6.6 E-45 E-4 X-ray abs. Coeff.2.5 E-5 cm E-4 cm -1 X-ray abs. probability10.4 ElectronicsHARPALICE

27/10/2004E.Radicioni35 Tracks and Background in the short TPG Intrinsic occupancy limit of the detector: N.strips/cluster size  ~ 200 –By exploiting correlations (a-la-compass) one could maybe do better 1 muon per  s  6 tracks in one “image” Number of background tracks (normalized per MHz imput photons) ~ MHz -1 Quoting Rikard’s computations: 22MHz of photons entering the tracker volume in the upstream spectrometer  if this rate is OK there will not be any trouble. Photon conversion in the HV membrane could account to the same number as conversions in gas  not much of a difference.

27/10/2004E.Radicioni36 Conclusions The TPG detector is operational in the HARP test-bed Placed an order for 2000 channels of the new electronics First results indicate performances at the expected level or better Several design parameters can be reviewed –Better gas choice  better resolution –Shorter detector  less material, straightforward construction, compact, could stay in shorter solenoid. –Faster drift time  less X-ray background –Better resolution More results from beam tests in the near future

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