Delayed wire chamber (DWC)

The delayed wire is the most commonly used supporting detector in the HGCAL beam tests at H2 beam line. The DWC is built in an aluminium case of 220 × 220 × 56 (mm), with two kapton windows of 110 × 110 (mm) and a thickness of 25 µm. The picture of DWCs is shown in Figure 5.4.

Figure 5.4: DWC setup

The supporting frame and the DWC is shown. There are 4 signal readout and a high voltage cable come from the back of the DWC. The functioning part is labeled by the red frame.

The DWC is a gaseous detector which works like the Multi Wire Proportional Chamber (MWPC). When a particle path through, the ionized gas will be accelerated by the high voltage between the thin cathode and anodes. At the end, the avalanche multiplication happens around the anode and the signal is readout. The DWC has 4 direction TDC(time to digital converter) readouts (top, bottom, left and right). By calculating the delay between x or y, the point where the particle penetrates is retrieved.

By using multiple DWCs in the beam line, the track of the particle can be recon-structed. The extrapolation of this track to the HGCAL prototype can serve as a refer-ence for studying position resolution as well as an event selection to reject the particle deviated from the normal trajectory. The resolution of the DWC in the H2 beam line is 0.2 mm, which is enough for the cell size of the sensor (∼1cm).

More information of the DWC can be found in [11].

5.4 Setups

5.4.1 2016 CERN beam test - configuration 2

In 2016, different beam tests have taken place at FNAL and at CERN. Here only the configuration 2 setup at CERN will be mentioned. The 2016 beam tests are based on CE-E prototype, the Figure 5.5shows the setup for configuration 2. The detector consists

Figure 5.5: 2016 setup (CERN config 2), plot from [6]

The X₀ of all the layers are calculated and labeled in the schematic plot.

Different materials of the absorbers are expressed with the in different color.

of 8 single module layers and the absorber layers. In addition, a lead block of 4.5X₀ is placed before the first module. From then on, a sandwich structure is repeated 8 times by the order of module-absorber. The absorber layers are all consist of 3 or 4 tungsten plates and/or a lead plate. In most of the detector, the modules are placed right side of the Cu cooling plate, while in layers 5 and 7 the module is put on the left side of the Cu cooling plate.

5.4.2 2017 July beam test

In 2017, 3 beam tests were taken at CERN: May, July and September/October. The July test beam is a milestone for the first system test to achieve the original design of HGCal. It combines CE-E and CE-H part of the HGCal detector and include the CALICE analogue hadron calorimeter (AHCAL) to collect the hadronic shower after the CE-H.

CALICE analogue hadron calorimeter (AHCAL) is a scintillator-based sampling calorime-ter with silicon PMT (SiPM) readout. The ASIC used is called the SPIROC, and the detector also has its own independent DAQ system. [13] The absorber between different layers are steel. The AHCAL is selected to act as the scintillator part of the official HG-CAL design. Although in the latter CE-H section the official design is a mixture of silicon and scintillator, it is still a nice trial to validate the performance of the material.

The full setup of this beam test can be found in Figure 5.6, while Figure 5.7 and Figure 5.8 gives a more detailed look to the silicon based prototype. In the CE-E, lead, copper and iron are placed as absorber (and CuW base plate). Iron absorber is placed in both CE-E and CE-H part of the prototype instead of tungsten. 3 silicon modules are placed in the CE-E as 3 single module layers, and 8 of the module are placed in CE-H with 2 single-module layer and 2 triple-module layer. The 3 module structure is made in order to contain the expected hadronic shower width.

Figure 5.6: 2017 July setup The full set up for 2017 July setup.

Figure 5.7: 2017 July CE-E, plot from Shilpi Jain.

The label EE is the old term used in the CMS phase 2 technical proposal.

Figure 5.8: 2017 July CE-H, plot from Shilpi Jain.

The label FH is the old term used in the CMS phase 2 technical proposal.

5.4.3 2018 June beam test

In early 2018, 3 modules are brought to DESY for beam test in order to obtain a better understanding for both the sensor and the electronics for Skiroc2cms 6” module. With the knowledge learned from DESY, 2 beam tests are taken at CERN in June and October.

June test beam is the first test to realize the full design of the CE-E in the HGCal technical design report (TDR) [7], with 28 layers single module prototype.

The absorbers are chosen to be 1X₀ in each layer, and ∼ 28 X₀ in total. The cassette structure is developed to contain 2 module back to back with good attach to the cooling plate. The cassette are constructed to keep roughly the same radiation length between all module layers, and the structure also make the transform safer. With such an effort, the prototype is finally ”compressed” into a 75 cm detector, with 28 layers of single module.

The aim for this setup is to test the behavior of various energy for electron and compare the agreement between data and Monte Carlo. The plan for October beam test will be having an order of 100 module prototype, with both EE, FH and the new AHCAL prototype ^†.

†Other than the AHCAL used in 2017 test beam.