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Spraying of Glass Plates for the DHCAL

Learn about the process of spraying glass plates for the Digital Hadron Calorimeter and the challenges faced. Discover the results achieved and the individuals involved in this important work. The data is presented from the RD51 Meeting at Argonne National Laboratory.

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Spraying of Glass Plates for the DHCAL

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  1. Spraying of Glass Plates for the DHCAL José Repond Argonne National Laboratory RD51 Meeting, by phone, April 13, 2011

  2. Digital Hadron Calorimeter: DHCAL Hadron Calorimeter for PFA application Resistive Plate Chambers as active elements Extremely fine readout segmentation 1 x 1 cm2 1 – bit resolution per channel (digital readout) Steel plates as absorber The DHCAL in numbers Each layer 96 x 95 cm2 38 layers in the DHCAL + 14 layers in the TCMT (tail catcher) Each layer with 9,216 channels Total number of channels 350,208 + 129,024 = 479,232 Status Construction completed Cassettes installed into the CALICE absorber structure at FNAL 2 successful test beam periods in October 2010 and January 2011 Currently taking data with the CALICE Silicon – Tungsten ECAL placed in front Additional standalone runs in June and possibly later… Jose Repond - Spraying of glass plates

  3. Signal pads G10 board Mylar Resistivepaint 0.85mm glass 1.15mm gasgap -HV 1.05mm glass Resistive paint Mylar Aluminum foil RPC design and construction Design Standard 2 plate design with glass as resistive plates Readout on anode side Outside of chamber coated with resistive paint to apply HV Challenges Maintain uniform gas gap (→ precision assembly fixtures) Bring the HV out as far as possible to rim, w/out break downs Provide uniform surface resistivity in the range on 1 – 5 MΩ/□ → Higher resistivity impacts the rate capability → Lower resistivity increases the pad multiplicity How to measure R□ Jose Repond - Spraying of glass plates

  4. Spraying glass Constraints on resistive paint Surfaceresistivity in the range of 1 – 5 MΩ/□ Easily applicable Resistivity not dependent on humidity (very important!!!) Paint Used commercial spray (LICRON) in the past, but new product not useful Identified some 2-component ‘artist paint’ → satisfies constraints Paint needs to be mixed appropriately and sprayed (with spraying gun) Spraying booth Built large booth to exhaust (non-toxic) fumes Movement of spraying gun controlled with step motors (~ 2minutes/plate) Spraying procedure Significant preparation needed: cleaning of glass, masking off rims, mixing paint, cleaning tools 1-botton operation Could spray up to 8 plates in one day Jose Repond - Spraying of glass plates

  5. Results Uniformity obtained by adjusting - Speeds - Distance to glass plate - Order of spraying - Air flow in booth MΩ/□ Jose Repond - Spraying of glass plates

  6. Overall values adjusted by - Adding water to the mixture - Modifying the ratio of the two components For the DHCAL + TCMT + spares needed ~400 sheets of glass Efficiency was poor ~ 60% Not all values plotted Environment (pressure, humidity, temperature) was poorly controlled. Better control needed for better reliability Jose Repond - Spraying of glass plates

  7. RMS related to mean value Note: not all plates measured and included Jose Repond - Spraying of glass plates

  8. And who did all the work… Daniel Trojand ANL + McGill Jacob Smith ANL + UTA Jose Repond - Spraying of glass plates

  9. A few nice events to conclude… Jose Repond - Spraying of glass plates

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