1. Test Beam Request for the Semi-Digital Hadronic Calorimeter

2. 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 :
cm absorber
+ 0.6 cm sensitive medium
1 cm2 transversal granularity
This is about 5(6) λI
and (442368) channels

3. 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

4. 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...)

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

6. 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

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

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

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

11. 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.

12. 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 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

13. 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

14. 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

15. 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