Minutes of DRAGON meeting 21st September 2004 1. DAQ (JP) We are unable to get gamma events properly out of the new VME system. HI events are read consistently. This does not seem to be a problem with a connection or cabling. The problem seems to be with the CAMAC driving unit. An additional CAMAC driving unit is required to test the DRAGON one against to ensure that it is functioning properly. (The CAMAC driver connects to the VME memory unit). G. Sheffer will be contacted about obtaining this module. As for buying a unit – they seem to be expensive: the old LeCroy model costs $2000, largely because this model is no longer manufactured or supported. All in all, DAQ upgrade has been going well until this stumbling block. JP estimates up until November or December before this DAQ upgrade can be continued, due to the scheduled running time and JP’s absence from the group in October. NB. With the new upgrade we can potentially achieve higher gamma rates (14KHz with practically no dead time). 2. POWER SUPPLIES (DO & DH): Klaus is back and will take care of the power supplies. ED1 anode power supply has been replaced. The dipole is conditioning at 5V/min. Sparks are still occurring occasionally causing the unit to trip on x-rays. The setpoint V reads 50% of the readback value on EPICS – why? There were major layout changes made to the new stack electronics boards designed to prolong their life and dissuade arcing. JDA: Do we need back up electronic components such as resistors etc, to prevent delays if stacks break down in future? After the period of initial Fall running, we plan to take the ED’s up higher in voltage. For the initial period they will be kept relatively low compared to what we have run previously (e.g. for 12C(a,g)16O). 3. PGAC (JC): The next idea for the PGAC-IONC setup is to try two foils (PPAC) instead of grids. In principle this should improve the timing qualities of the system. P10 gas was tried with the PGAC (P10 is Argon with 10% Methane). However the Argon seems to be much slower (i.e. has a significant drift component) than Isobutane. This implies that the speed of the gas due to such a drift component does in principle matter with the PGAC setup, i.e. that it is not a pure avalanche counter. Therefore a faster gas such as Freon may help matters. 4. ION CHAMBER (DO): The Ion Chamber has a new ‘blast chimney’ which will be finished by the end of the week. Everything except the control should be completed by this time. Beamlines are going to put the ‘cork’ on top of the ‘chimney’ this week also. (If the flammable gas inside the chamber ignites, the large increase in pressure will ‘pop the cork’, which will safely explode within the confines of the blast shield, preventing possible catastrophic damage to the Ion Chamber and surroundings). 5. Si DETECTORS: CV to check on status of DSSSD detectors for upcoming runs. How many do we have? We may need to order a new one now! The detector with the broken bond wires needs to be sent back to Micron on Warranty, since the damage was not caused by mishandling by DRAGON members but by a possible defect in workmanship. 6. UPCOMING BEAMTIME (DH): See page 9 of the attached PDF file for the October run plan with 21Ne(p,g)22Na. The DAQ will work for this run in its present capacity. The ROOT GUI needs to be modified in order to view spectra for this run. Do we need the MCP for this run? We can potentially increase the bias voltage on the DSSSD in this run to improve the timing. (See page 5 of PDF file for CV’s info on DSSSD timing versus applied bias voltage). Aside (JDA) – 22Mg mass: ISOLTRAP and ARGONNE have separately measured the mass of 22Mg. Their results agree with the DRAGON implied mass from our 21Na(p,g)22Mg resonance measurement. The state previously though to have been at 5714 keV in 22Mg was observed by Gammasphere at the FMA as 5711 keV. 7. CONTROL SYSTEM B. Laxdal has changed time constant on FC4 for improved fast current measurement. DH showed the new logic for the Ion Chamber/DSSSD gas handling and vacuum system. This can be seen on pages 7 and 8 of the attached PDF file. 8. AOB NSERC grant applications were discussed. JC’s 22Na experiment would require an equipment grant. Equipment on loan: we currently have 2 delay-line amps on loan from the pool for the elastic monitors. We also have the two NaI detectors and their preamps on loan. We should take measures to acquire our own equipment for these items. We require a quad TFA for the PGAC setup. Moving the MCP upstream was discussed. This would cause focusing problems – but could be investigated with GEANT. In order to operate the MCP – PGAC – IONC at same time, require 9 preamps. G. Sheffer only has two extra available. For future DAQ system, would like to have two crates at both ends of DRAGON (are those the Jaws and the Tail?), optically linked, with VME ADCs and TDCs for the DSSSD. We would need 3 of each. CV presented results from the Isobar Separation experiment, which can be seen on pages 1 to 5 of the attached PDF file. We are required to submit an REA for the IONC new gas system.