1. What canlearn from about Ken Livingston, University of Glasgow, Scotland

2. g8 summary coh. peak (GeV) 2.07 2.25 unpolarised triggers (M) 1400 350 100 Increased world data set on  by x 100 for polarised photons in the 1.75 - 2.25 GeV range. crystal thickness50um angle to beam~1mrad beam current7nA current status calibration almost complete pass 0 cooking to begin in ~2 weeks

3. g8 school report card for coherent bremsstrahlung componentdesired qualities(personal) score / 10 photon beam diamond goniometer collimation tagger stable, low emittance thin, uniform monocrystal high precision (<10 urad), reliable tight, easily positioned, (active ? ) highly segmented, < 2ns timing res. fast feedback via scalers 6558665586

4. goniometer and diamond radiator goniometer problems oversize no feedback ? got lost, stuck for g8b goni to get "full service" 20 um diamond radiator problems coherent peak jumped around in an unpredictable way for g8b find out why goniometer installed by GWU group

5. tagger and e-counter scalers a few noisy channels... 2 weeks later Tagger had major upgrade + ecounter scalers. Commissioned at start of g8 run period tagger problems some teething troubles with upgrade, but generally performed well. rate in coherent peak limited by big T counters for g8b new tagger electronics, scalers can be gated by downstream detector

6. coherent peak instability problem with 20um crystal coherent peak "jumps" around by very large amounts. possible reasons crystal damaged by grinding to 20um from original 100um beam not stable enough (ruled out by 50 um results) goniometer (or other) vibration crystal "bowed" on mounting wires - to be tested with laser (next week)

7. electron beam at 5.7 GeV in Hall B beam problems Standard quadropole for beam tuning in hall B is downstream of goniometer. Coherent peak is worse for "para" than "perp" due to non-symmetric beam. Angular divergence of beam dominates (lose advantage of thin crystal) for g8b A new quadrupole to be fitted upstream of the goniometer

8. conclusion Overview of g8 g8 was the first run group to use linearly polarised at Jlab Very successful first run period. problems Several minor problems due to first use of system, easily fixed for g8b Problems due to "retrofitting": tagger and beam focussing to be improved for g8b Outstanding problem - 20um crystal Hall D big advantage Designed specifically for coherent bremsstrahlung. Should be able to avoid most hall B problems. problems Anticipate using a 10um crystal. Still need to understand the "jumping peak" problem. ** Important to decouple coherent brem source from main experimental DAQ