DRAGON Meeting Minutes for Sept 23/03 Present: Art Olin, Mike Trinczek, John D'Auria, Cybele Jewett, Dave Ottewell, Nicole Chorney, Zhihong Li, Lothar Buchmann, Mike Lamey, Peter Machule, Aaron Bebington, Goetz Ruprecht, Dario Gigliotti (recorder) 1)AB (See Fig 1 for details) Reported on recent developments of the GEANT ionization chamber simulation as submitted by AB for the minutes. With the transfer of files from lin01a to ibm00, modified files within my directory were lost, being replaced with older versions. Not knowing this at the time, I had to go through the painful process of putting the ionization chamber back in to the GEANT DRAGON simulation for 13C. Peter Gumplinger sorted out the problem with the ONLY/MANY flag on GEANT volumes, and I was told that mother and daughter volumes are allowed to overlap, but if two daughter volumes overlap, then they are given the MANY flag. Therefore, all six volumes that make up my simple ionization chamber are given the ONLY flag (see page 1 of attachment). He also told me the best way to simulate the ionization chamber, holding all five daughter volumes within a vacuum mother volume, for example. The mylar window (ICMW) is placed at the end of the vacuum tube (ICVT), which is placed in the aluminum entrance tube (ICET). The isobutane gas dead layer (ICDL) is placed at the front of the isobutane gas box (ICGB), which will eventually house all four of the ionization chamber's anodes. Both ICGB and ICET are then placed back-to-back in the vacuum mother volume (ICAC). Hart Sprenger measured/calculated the positioning of the ionization chamber with respect to the DRAGON, and found a distance of 61.96cm from the final slit to the mylar window. The ionization chamber was eventually put into its correct position within the DRAGON simulation, and the first few runs were showing that the recoils were not making it passed the end of the entrance/vacuum tube. After a lot of searching, the problem was found to be a definition of the isobutane in the GEANT code. Once fixed, I run the first proper simulation (see page 2 of attachment). This time the recoils made it in to the ionization chamber, but they all seem to stop dead around the anode 1 region (see page 3 of attachment). Also, I found by running in the interactive version of the simulation, that the recoils are not "seeing" the mylar window. This is probably due to fact that the step sizes are not small enough to see the 0.000094cm thick window. Future plans: a) to find out why the recoils stop where they do (maybe be the pressure), b) to change the final energy spectrum to recognize the recoils in the ionization chamber, c) to get the simulation to register the mylar window. 2)AO,MT Report that CVS is available for GEANT development of the DRAGON simulation. This is a program that allows multiple users to work on code development for the same program but gives reports on any changes that have been made to other programmers. 3)AO (See Fig 2 for Details) Reported on GEANT simulation results of DRAGON acceptance sensitivity due to angular and positional changes of incoming beam to the target Simulation was done for nominal tune taking into account energy loss of recoils from centre of the target a) 0.89 MeV 12^C beam gives 45% recoils at end b) displacement of 3mm in x gives 39% of recoils at end c) displacement of 3 msr in incoming angle gives 38% recoils The statement was made (LB) that where the losses are should also be presented 4)JR (See Fig 3. for details) Ongoing report on the GIOSP simulation studies in search of a new tune to increase DRAGON acceptance The points shown on the curve determine the lowest energy that can be run with this "broad tune" which will just fit the size of the detector proposed in the experimental confirmation of the "broad tune" 5)D0 Solid target commissioning -Scintillation in the solid target can be seen from mylar foil but not C -Energy loss through the C foil is as expected -Can see illumination of the solid target in CCD camera. It may be possible to see if a foil has broken by this method. -Elastic monitor in new solid target mount is not yet commissioned A -A 25 mrad pumping tube will be built for the final pumping stage 6) ML (See fig 4 for details) Report on MCP studies -studies were done by using a buncher to time focus the beam -MCP efficiency found to be ~93% -below are further details of the attached fig4 from ML The second and third parts of fig 4 are from 20Ne beam in Aug. I just showed them to remind everyone of a problem from before (pg2 top = rftimeto DSSSD, bottom = MCP time to DSSSD). pg 4 is 20Ne 400KeV/u beam from last Friday. One thing I forgot to mention in the meeting is that we tried changing our "brown" timing box with a TFA and a CFD and got a fwhm of 2.7 ns. Thus I wanted to say that in fact the brown box does work better. pg 6 is from a 1GHz bandwidth scope which I needed to look at the rise time, and confirm that it was fast. 7) Other business ED1 conditioned to 80 kV. CJ reported briefly on her trip to Oak Ridge where a 12C(12C,2n) reaction was done. Recoils were detected into a 3 anode ionization chamber. Gammas are detected in Ge ball which has BGO detectors added for Compton suppression There is a mini shutdown for the next 2 weeks after which beam should be available to do the confirmation of JR's simulated "broad tune"