1. José Repond Argonne National Laboratory
DHCAL Developments
José Repond
Argonne National Laboratory
CALICE Collaboration Meeting
Max-Planck-Institute, München, Germany
September 9 – 11, 2015
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2. A) 1-glass RPC validated
Resistive paint
Signal pads
Mylar
Aluminum foil
1.1mm glass
1.2mm gas gap
-HV
A) 1-glass RPC validated
Measurements with Test Beam
Rate capability better than 2-glass
Pad multiplicity close to 1
Chambers work in showers
Measurements with Cosmic Rays
Published in JINST 10 (2015) P05003

3. B) Measurement of the rate capability
Three different RPC designs
1) Standard 2-glass design (20x 20 cm2)
2) 1-glass design (23 x 48 cm2)
3) 2-glass design with semi-conductive glass (20 x20 cm2)
Glass Model S8900 from Schott Glass Technologies Inc.
Readout
Standard DHCAL readout (1-bit)
Data taking with external trigger (finger counters)
Set-up in beam
2 chambers for each design (6 in total)
Spaced about 5 cm apart
RPC
design
Number of glass plates
Area A
[cm2]
Bulk resistivity ρ [Ωcm]
Total thickness t
of the glass
[cm]
Conductance per area of the glass
G =( ρ·t)-1 [Ω-1cm-2 ] 1 2
400
4.7 × 1012
0.22
1.0 × 10-12
1536
3.7 × 1012
0.11
2.4 × 10-12 3
6.3 × 1010
0.28
5.6 × 10-11

4. Measurement in Fermilab Test Beam
Efficiency/pad multiplicity versus beam intensity [Hz/cm2]
Beam
120 GeV protons
Defocused to provide larger beam spot: 2σx × 2σy = 2.0 × 1.6 cm2
Intensity varied from 10 to 113,800 Hz/cm2
Beam extraction not uniform over spill at low intensities, much better at high intensities
Systematic uncertainty in beam intensity from extraction (dominant) and beam spot

5. Results I
Comments
As expected, with decrease in efficiency with increasing rate
1-glass design better than standard RPC
Semi-conductive chamber better than 1-glass design
Pad multiplicity close to unity for 1-glass design
Pad multiplicity high for semi-conductive chamber (thicker glass)

6. Results II Determine Rate I50% at which RPC 50% efficient
Compare different designs
Fit to empirical function
I50% = a + bH + cH3
with H = 1/log10(G)
Extrapolate to
1 1.1 mm semi-conductive glass RPC
→ I50% ~ 25kHz/cm2
arXiv: : Submitted to JINST

7. Future DHCAL Activities
Funding for the DHCAL
Has been terminated on October 1, 2015
Future activities
Plan to perform detailed, analog measurements of the signal charge
Still working on publishing results from test beam runs