1. Testing of C-layer bottom hole counters A.Ito, J.Negret, B.Satyanarayana

2. June 30, 2003D0 Muon Meeting2 Introduction Wide 92.270” X 33.282” 18 deep grooves 6 fibers per groove Narrow 92” X 15.75” 49 flat grooves 4 fibers per groove Total 8 counters; 4 wide and 4 narrow type BC404 0.594” thick scintillator and BCF-92 WLS fibers Readout by twin Meltz PMTs

3. June 30, 2003D0 Muon Meeting3 Tests Radioactive source –Mapping the counter with source –Comparison of counter responses to the source –Detailed scans of the counters Cosmic tests –Counter efficiencies for cosmic muons –Time delay measurements Response to LED pulser input All tests done with the same set of PMTs

4. June 30, 2003D0 Muon Meeting4 LED pulser tests Using two fibers from LMB driven by SLP simulator LED drive amplitude (DC+AC)  12.7V Average pulse height = mV

5. June 30, 2003D0 Muon Meeting5 Cosmic tests Efficiencies for cosmic muons: > 99% Time difference in response between the centre and the edge of the counter: ~5.5nSec Problem with cosmic showers Trigger modified to include a veto

6. June 30, 2003D0 Muon Meeting6 Summary No problems noticed with counters Marked PMTs installed on the counters PMT voltages set to produce minimum of 100 mV signal anywhere on the counter LED pulser tests are also repeated Counters should be ready to go in a day or two