1. E-165 (FLASH) Status 8:00am 6/13/2004

2. Thick Target Program Primary goal is to measure the fluorescence light output at different stages of shower development Uses electromagnetic shower from FFTB 28.5 GeV pulses to simulate air showers

3. Status as of 8am 6/13/2004 FLASH optical chamber with PMT N1-N6 ready for action Response/Aperture of chamber mapped and demonstrated to be stable against mechanical flexing Have been set up for neutron background tests using spare PMTs B1, B2 since Thursday evening

4. Last 24 hours No beam yet to FFTB: –Proceeded with the wiring preparations and took data for stability of PMTs B1 and B2 –Vacuum difficulties have been mostly corrected, last update is a problem upstream –Charlie implementing online data summary program We are now sending data routinely to Utah

5. Stability Test Results Analyzed data from run 1989 (collected from 21:53 to 02:33 - 4h 40m) and 1990 (collected from 02:33 to 06:55 – 4h 22m) Using 500 photo-electrons to be in channel 1363 (higher gain than expected) Found collected data for ADC/PED channels From theory, the width was taken as the square root of the value multiplied by the α-factor of ~1.2 –The experimental values hold well with the theory –The values are in agreement between runs

6. Stability Test Histograms Run 1989 Channel 2: 156 ± 16 photo-electrons Channel 3: 128 ± 13 photo-electrons

7. Stability Test Histograms Run 1990 Channel 2: 157 ± 16 photo-electrons Channel 3: 130 ± 14 photo-electrons

8. Options 1.When BCS system is ready we will proceed with neutron background tests 2.High Current beam over the weekend: we will position the “dog leg” (without the main optical chamber) with a shutter and no shielding to look at beam-induced backgrounds

9. High Current Beam Background Run REQUIRES NOTHING in the BEAM PATH itself!!!! The beam background will allow us to make a thorough checkout of the PMTs, readout, and LED monitoring systems Also will let us exercise the data handling system (export to collaborating institutions for monitoring) and online analysis

10. Today? If BCS system work should continue into Monday: –May request “thin target” run at medium current (~10 9 electrons per pulse) –Alumina targets will be retracted –The center of the main optical chambers have 4” diameter holes with thin windows and will represent about the same amount of material as we had during the thin target run in 9/2003

12. Many Thanks Again: we cannot give enough thanks to the experts and our friends at the MCC for working late into the night to help us get going… Your help and hard work is VERY appreciated by the FLASH group as a whole Thank you thank you thank you….