Test Beam Request for the Semi-Digital Hadronic Calorimeter

The Technological prototype Goal : to build a prototype of very compact, ultra-granular HCAL using GRPC with semi-digital embedded readout electronics PFA The prototype should be as close as possible to SDHCAL concept proposed for ILD Barrel Module gas  Self-supporting mechanics  Minimized dead zone  Minimized thickness  One-side services  Power pulsed electronics Beam Beam The prototype will be made of 40(48) units. Each unit is made of : 1.5+.5 cm absorber + 0.6 cm sensitive medium 1 cm2 transversal granularity This is about 5(6) λI and 368640(442368) channels

Advantages of a semi-digital gaseous HCAL Gaseous detectors : Homogeneity, granularity, cost-effectiveness Power-pulsed semi-digital readout : A binary readout digital HCAL using GRPCs was already built and proved to be successful. However, at high energy the shower core is very dense simple binary readout will suffer saturation semi-digital readout (2-bit) can improve the energy resolution. GRPC Avalanches 1 cm2 pad

History: Small GRPC The SDHCAL group of the CALICE collaboration have conducted extensive TB to check: GRPCs performance : Both small, intermediate and large GRPCs were tested Readout Electronics : The essential part of the readout electronics chain was tested Successfully tested. (ASICs, DIF...)

Large GRPC and cassette construction : Many evolutions….. 144 ASICs= 9216 channels/1m2 1 pad= 1cm2 , interpad distance = .5 mm

Prototype Construction The construction of the prototype has started two months ago and is expected to Finish end of March. ASICs and DIFs : all tested and calibrated. PCBs are being produced and cabled GRPCs components are available. Assembling is ongoing (20 chambers are already built) DAQ hardware components are available. Software development is ongoing Mechanical structure construction is ongoing. Gas distribution system is ready. It was built according to CERN safety department recommendation

Assembling procedure Final thickness : 11 mm Clearance : 2 mm in Z 4 mm in X Insertion test Final thickness : 11 mm

Cassette validation 2 full cassettes were successfully tested at T9-PS May 2010 and H4-SPS in September 2010

Cassette to be inserted in the Mechanical structure Services racks The SDHCAL prototype scheme

Strategy : Test-Beam we need a special movable and rotating stage capable of supporting up to 10 tons. We need also to use a TB line which provides low energy pions. These two conditions limit our choice. Contact with ATLAS Test Beam coordinator was established to see if we can use the ATLAS stage on the H8 line. This line is one of two lines able to provide hadron beam as low in energy as 2 GeV.

Test-Beam program First period (July-August): Three kinds of particles beams will be requested 1- Muons: To control the detectors and estimate their efficiency in situ. To align precisely the detectors inside the HCAL 2- pions: To study energy resolution in the 2-100 GeV range. 3- Electrons : To study the HCAL response to a pure electromagnetic particles In addition to energy scan, there will be angle scan as well as a threshold scan. The latter allows to select the best values for a better energy resolution

Test-Beam program Second period (October-November) : The aim of this test is to have a deep understanding of the hadronic shower behavior once the detector response is well understood. We would like to have by that time 48 units (as for the modules proposed for ILD (56 λI)) . We intend also to have a combined test with the CALICE ECAL detector which represents an additional λI

Power-pulsing test In 2010 the power-pulsing scheme was tested for the first time with the 3-Tesla H2 magnet Trig_ext (Lemo1) Enable Acq Enable PP Vth2 Power On Power Off 50 µs Time to previos event (ms) PP is on during 2 ms every 10 ms rather than every 200 ms for ILC PP ∆t>100µs PP ∆t>1000µs No PP ∆t : Delay of data taking with respect to PP

Power-pulsing test In the parasitic mode very short time was dedicated to this test in low density conditions (< 100 Hz/cm2 to have efficient GRPC) So we need more statistics to confirm the nice results in all possible conditions (orientation with respect to magnet field, high voltage, thresholds....) The test will be also used to check the DC-DC module behaviour in a magnetic field of 3 teslas Two weeks seem necessary