Minutes DRAGON meeting 2004-08-17

Present: GR, JP, MT, JC, LB, KO, AR, CR, DFOT,PM, AO, AH, CV (recorder)

1. DAQ:  JP reports of changes, 2 crates  HI and Gammas
       new stuff running on JP's Laptop, old stuff still on isdaq04
       maybe some help need from Constantin later on
       major step should be front end running on new stuff 
       JP needs help for C++ stuff, JC volunteered

2. Power Supplies:  DFOT reports that PS for sextupoles S3, S4 are changed over with Q9, Q10,  polarities will be checked

3. YSLITM:  PM measured infinite resistance, whereas previously 60 Ohm where measured (JC mentioned 180 Ohm under Vacuum)
       all wires looks ok
       maybe surfaces which are closest to the slits should be wrapped with mylar, tape or paint

4. ED1: Problems with ED1, 40kV with 10mA
       PS switched - no change, must be something wrong inside stack

5. PGAC:  CV reports about testing current setup with different Voltages, Gas Pressures and 
       alpha and fission sources, rise time of signal not better than 10-15 ns (same as some years ago)
       tried to change the gap between grids to see some influence
       3 anode wires were broken during disassembling, but should be fixed later this afternoon, there are also plans to try a foil for anode plane
       JC reports that PM and SusiQ are setup to measure timing resolution

6. IC interlock:  DFOT reports about planned changes of IC gas handling system
       2 systems: gas (not in APEX) and vacuum of IC/DSSSD box and chamber (will be included in APEX)
       pg 5 will be cleaned up and split into 2 pages, one for IC and one for DSSSD
       automated needle valves are expensive, cheaper way is using a automated solenoid valve and a manual needle valve parallel 
       CR said there is a new description on the web for gas in by ML

7. BGO efficiency:  AR reports about comparison between measurement and GEANT simulation
       Y-88 sources were used inside the target box with BGO array closed
       (DG Cs-137 source was not used since dead times are around 90%, for Y-88 around 50%, still high but manageable)
       Spectrum of detector 14 shows a good fit (minutes040817.pdf pg1), 21 a bad fit (minutes040817.pdf pg 2) fit too broad, area maybe underestimated
       In GEANT simulation with lead shielding, new GEANT without lead shielding planned
       Measurement and simulation agrees rather well (minutes040817.pdf pg3)
       Pileup (pdf pg5) was included makes it even better (minutes040817.pdf pg4)
       DG tries to run GEANT with the 2 lines of Y-88 to see contribution of sum peaks

8. 21Na(p,g):  MT presents new fits, all points are now included, no reason found to throw away data points (minutes040817-2.pdf) 
       Charge fraction measurements are included (old data are based on 21Na measurements)
       Uncertainties of energy of incoming beam included (blue fit, red fit without)
       incoming beam based on KO&DH procedure using FC4 and elastics.
       Data are now comparable with CR's data 

9. 21Ne & slit closing:  KO presents results by MA on GEANT simulations using 21Ne data (instead of 12C(a,g)16O)
       no significant reduction seen in simulation whereas in the measured data there is a reduction (minutes040817.pdf pg 7)
       possible explanation: simulation only of recoils, but measurement contains a significant fraction of leaky beam, too. Suppression of only leaky beam?
       AO beam spot is larger than in simulation

10. Goodbye lunch for summer students:  AR and KO should present a plan for the next meeting, tentatively scheduled for Friday, August 27.

meeting ends at 11:40