PoS - Proceedings of Science
Volume 380 - Particles and Nuclei International Conference 2021 (PANIC2021) - Development of accelerators and detectors
Recent developments of the SDHCAL prototype
G. Grenier* and  On behalf of the CALICE/ILD SiW ECAL group
Full text: pdf
Pre-published on: March 10, 2022
Published on: May 24, 2022
After the construction and successful operation of
the first technological prototype of the Semi-Digital Hadronic
CALorimeter (SDHCAL), developed within the CALICE collaboration,
new R{\&}D efforts have been initiated
to fully validate the SDHCAL option for future
experiments proposed for the ILC and CEPC colliders.
The SDHCAL is a sampling hadronic calorimeter using large Glass Resistive Plate Chamber (GRPC) as
active medium with embedded readout electronics. The GRPC prototype
size is 1~m$^2$ while future detectors require GRPC detectors
with scalable length up to 3~m long (0.9$\times$3~m$^2$).
The readout Printed Circuit
Board (PCB) consists of 1~cm$^2$ copper pads on one side and
64-channel HARDROC readout chips on the other side.

The design of such large size scalable detectors has been addressed
and has required rethinking the gas flow in the GRPC in order to
maintain detection efficiency and spatial response homogeneity. The
readout PCB was also redesigned to make it scalable in
length and more tolerant of ASIC readout failures.
It now uses the latest version of
the HARDROC readout chips series.
To deal with the maximum production size of a PCB with 8 layers,
an ingenious scheme with several PCBs connected to each other by tiny, flexible connectors has been developped.
A new DAQ interface board with an optimized geometry to fit the
requirements of the ILD detector, can handle a PCB area
up to 2.76~m$^2$, sufficient to
cope with the GRPC maximum size in ILD.
A new cassette, as part of the calorimeter absorber, is being
designed. The main challenge is to ensure the rigidity and uniform
contact between the GRPC and its PCB. For the ILC detector, the
ILC beam time structure is used to power-pulse the ASICs to
keep the power consumption low
enough to avoid cooling the PCB. For the CEPC, the continuous
operation of the accelerator implies adding cooling capacity to the
designed cassette structures. In addition, tools to handle the new cassette are being finalized.
Finally, the way to manufacture the mechanical structure
to support 3~m long GRPC with the needed improved flatness has
been solved.
A first fully assembled prototype
of 2~m$^2$ with 4 GRPCs is expected to be ready in year 2022.

In addition, new developpements to replace single gap GRPC by
multigap GRPC coupled with fast timing electronics are being
pursued. A time resolution better than 50 ps is achievable. This
will allow to follow the temporal evolution of the hadronic showers
developing in the calorimeter.
In parallel, the first SDHCAL prototype has been extensively tested
in beam test facilities. Refined analysis techniques are being
developed to improve the energy and shower reconstruction. The latest analysis developments cover techniques
to improve the spatial uniformity of the response and a better
treatment of the particle incidence angle in the energy reconstruction.
DOI: https://doi.org/10.22323/1.380.0095
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