DRAGON Minutes										24 August 2004

Present: DO, DH, JC, AH, AR, KO, PM, DG, GR, JP, and CJ (recorder).

JP: 	-His laptop died, but he backed it up on Friday, so he recovered all of the data.  
		+He does need a new hard disk.  
		+Peter Machule can probably replace it with a 20 GB hard disk.
	-The DRAGON ROOT code is now running online.
    		+All of the scalers and gammas are in ROOT.
    		+We can now acquire data in ROOT.

Magnet power supplies: -Reineger is away, and nothing appears to have happened.

PM: 	-He will work on testing the Y-SLIT.  
		+It is probably okay.
        -For ED1  
		+He is ordering new boards.  
		+About 30+ of the resistors are gone.

JC: 	-He changed the planes to make the PGAC thinner.  
		+The thinner configuration was worse timing.  
		+Changing the anode wires helped the timing.  
		+They are adding a foil plane.  
		+JC installed a weak fission source Cm(Cf), and took a spectrum with it.  
                 The result was that the time resolution appears to be better.
		+The resolution JC obtained with the Cf source, wires, and no foil plane was
                 about 1.2 ns.
		+The problem with the Cf source is that not all of the fission fragments make 
                 it into the scintillator, which acts as the start of the PGAC-scintillator detector.

AH:	-AH tested a dE-E Si-strip detector, which has 5-strips and a broad strip that sits behind them.
	-The dead layer between the dE and E strips eats up energy.  
		+AH is going to measure the dead layer thickness.  
	-Most events seem arrive, and cause four or five strips to fire at once, which is bad.  
		+There may be cross talk between the pre-amps in the electronics board.
		+Most likely, this caused by a faulty board.
		+Bill Roberts is looking into the problem.
		+Catania will try to reduce the dead layer thickness.
		+A method which would resolve the dead layer issue would involve using only dE
                 part of the Catania detector, and some other detector for the E measurement.
		+An estimate of the dead layer thickness is a fews microns.  It could thus even
                 be larger than the dE.  Since we need to make low energy measurements, it 
                 presents a problem.
		+JC raised the possibility of an undesired electrical connection between the pads.
		+The noise level produced by the detector is low, and therefore not the cause 
                 of the problem.
		+Catania can make the detector larger (approximately 3 or 4 strips by 8 strips
                 compared to a DSSSD)

DO:	-DO reported on plans to improve the gas handling system of the IC.
	        +Robert Oppenshaw has returned.
		+They are installing interlocks and automated valves to prevent the ionization 
                 chamber window from bursting.
		+Some valves will be removed.
		+DH recommended submitting an REA.
		+Limiting the pumping speed is the key to preventing a window from rupturing.
		+DO is going to try to create separate pump up and pump down pages for the same
                 gas-handling devices.
		+PM suggested adding hardware switch to indicate DSSSD vs ion chamber mode.

AR:	-Their 12C(a,g) analysis involved simulating the data in GEANT, and fitting the data to 
            the 3.439 MeV and 6.917 MeV peaks with the purpose of looking at BGO efficiencies.
		+The 6.917 MeV peak shifted from crystal to crystal.
		+Three runs went into their analysis.
		+Charge state distribution measurements were only done for the 5+ and 6+ charge 
                 states, and thus a charge state fraction of 10% was assumed for the other charge
                 states.
		+DG said that the gains of the BGOs can drift over a day or over weeks.  There is
                 no general trend in the BGOs' gain shift behavior.
		+A discussion of how to improve the Gaussian fit to the peak data ensued.
		+DH: We want to be able to subtract the tails of high energy gamma ray peaks from
                 the peaks of low energy gamma rays.