PrimEx meeting minutes 12/15/00

Ashot Gasparian

Items for March April Installation Dipole Vacuum box target mechanisim exit window superharp Dipole power supply (new one) Pair Spectrometer (stage I) TAC (w/ moving mech.) (shot down by Bernhard. Possibly move to June Maint.) HYCAL protoype (shot down by Bernhard. Possibly move to June Maint.) PrimEx Major Goals for 2001 Test of photon flux control (~1%) Pair Spectrometer (Stage I) Tagging system (upper 20%) TAC (needs to be upstream for accuracy, but we're unlikely to get that put in for tests). We should try testing using already exisiting downstream TAC Test of Trigger Rates in HYCAL hycal prototype tagging system Start Construction of HYCAL Hall-B Schedule Official Accelerator and Experiment schedule Important point is that there are no facility development days scheduled. There are a few mantainence days, but no beam is available during these.

Dan Dale

Pair spectrometer detectors Fringe fields at position of Pair Spectrometer are 50 to 100 Gauss at an angle of 27 degrees B-field inside the tube is about 5 microTesla (the sensitivity of the tube is about a factor of 10 greater than this so we are safe) After experimenting with different light guide shapes, Dan came up with a trapezoidal design. Scintillator, light guide, and PMT will be glued together as a unit to so if a something goes bad, the whole unit will be replaced. Magnetic tube shielding will be rigidly attached to the support, but there will be a little play for the tube inside. Incoherent Brehmstrahlung (should we be concerned?) Gil, Oset Nucl. Phys. A580 (1994) 517-537 It's unclear wheather we'll need to worry about this or not Dan Sober suggested bremstrahlung from electrons is a bigger problem Calculations show that we might be able to see this effect with the Pair Spectrometer and a scintillating fiber detector behind it. Pair Spectrometer Electronics TDC's on every channel with a prescaled PS trigger would provide lots of potentialy useful (if not vital) information

Abdellah Ahmidouch

Dipole field Mapping Mapper moves in x and z (but not in y) Y mapping will be done by stacking three hall probels vertically Software work is still needed A suggestion was made to include a reference point that can be used to re-align the mapper without surveyors Mapping in test lab will likely start in Feb.

Sam Danagoulian

Superharp Engineering of fork is delayed until after they finish the target ladder Expect to be ready for installation in April (it was not clear if this was going to officially get on the agend or not) Software for controlling it is done Interface with DAQ is not finished

Eugene Pasyuk

HV for all E-counters Previously, 4 E-counter detectors shared a single HV channel. New supplies are being installed to give each of the 384 E-counters its own HV channel Two new LRS1448 crates are already installed in Hall-B (no cards) Recabling is partially done (96 of the 384) Old bases have been partially replaced with new design A number of replacement tubes for the E-counters have been ordered T-counter TDCs Problems with the timing range and physical cable delays caused the PrimEx beam test in July 2000 to lack T-counter information. Currently: LRS1875A for T-counters (common start only) LRS1877 for E-counters (common start or common stop, but not precise enough) Possible replacement: CAEN V775 which can work in common stop mode and has similar precision to LRS1875A

Rory Miskimen

Targets 2-dimensional control on target ladder positions 6 target slots for: C Sn Pb Thin (10^-5) convertor for PS cross-wire blank Frames are about 1 1/8" squares with circular holes. Targets are sandwiched between two pieces that are bolted together so as to not deform the targets (some will be rentals) Veto UVA has some paddles that may work well for us. Rory has been in contact with Donal Day, but UVA has not committed yet. These already have phototubes XP22?? Dimensions are : 11 x 1/2 x 1600 cm^3

Liping Gan

July beam tests Light leakage due to transparency of wrapping material near tube Non-linearity due to PMT high voltage divider Bench tests of PMTs and dividers A plot showing how the rise in gain with rate for XP1911 tubes can be significantly reduced at large rates with externally supplied voltage (~300V) to last three dynodes was shown A simliar plot made from russian tubes was also shown expressing a much less significant effect Temperature control does not help the gain/rate correlation Degree of high rate problem is dependant on individual phototubes Dynode baseline dependance on rate was measured to be roughly 1mV per 100kHz from 100 to 300 kHz Modified base design increases dynode signal to 50% of anode size to accomodate trigger.

Ashot Gasparian

HYCAL Prototype (items it will test) Rates vs. Photon beam intensity (used to determine beam hole size) Mechanical Tests: Cabling, connectors, light monitoring system Tests of transition region between Pb-glass and PbWO4 Test of temperature control system (including Pb-glass modules) Beam tests of detectors (position and energy resolution) The plan is to build a new HYCAL prototype by end of May.

Sam Danagoulian

Light Monitoring System Work has continued on this with some details still to be worked out System will incorporate laser and/or LED light sources

David Lawrence

Electronics A committment letter has been sent to the US CAEN sales representative for 4 mainframes, 25 cards (48 0.5 mA channels each) and 1 card (28 4mA channels). This will be enough channels to supply the entire calorimeter and veto. This also includes spare modules. The total cost is around $135K. Report from a discussion with the Hall-B online group yielded the following suggestions: Strongly advised to use a Trigger Supervisor module (desgined and built at JLab. This is a very fast, semi-intelligent VXI module that can accept multiple trigger inputs and distribute the signals to all other digitization electronics in the Hall. Suggested we use VME scalers since code already exists for these in the Hall-B online system. Using something not already supported will require significant time/expertise to incorporate. The JLab electronics pool has spare VME crates and scaler modules we could borrow so this costs us nothing. Programmable Logic Module: Hall-A experienced some strange internal deadtime problems with an LRS2373 module. This is module is basically a RAM chip and is very similar to the C542 module currently in the plan for the PrimEx trigger logic. Dave will contact Hall-A person and CAEN to determine if this will be a problem for us. Connector Types and Cabling One or many connectors? Saftey says it's doable, but will require us to identify a specific connector before we can go up to the next level for approval. How to route the cables from HYCAL to the electronics? (PC boards, trays, wire frames,...) A conceptual drawing was shown for how a wire frame might be used. Eugene Pasyuk suggested some type of cylindrical structure which maximized the real estate available for connectors. This will be looked at as well. Fastbus Power supply: One of the two fastbus power supplies we got from Fermilab has significant noise problems on at least the -5.2V module. Dave will work on getting that fixed. For now we only need one supply for our test setup. Need detalied testing of: Analog Delay chips Memory Lookup units High rate capabilites of UVA120/UVA125's

Doug Tilles

April Installation schedule Transport magnet on April 9th to Hall Install lower yolk on 10th Coil packages on 12th Upper yolk 16th (Monday) Vacuum box 17th (possibly) Pair Spectrometer detector support 18th magnet power supply and LCW connections 11th finish around April 20th All of the magnet installation (about 6 days) can be reduced to 1 day if it can be installed in one piece. Doug will weigh the magnet to see if it is under the 20 ton limit of the Hall-B crane.

Mark Ito

Dipole Power supply Scott Higgins of accelerator division will handle software control Bill Merz is interacting with the vendor (Danphysik) and answering any questions they have from our end No word on delivery schedule so we assume it is still set for Feburary Doug Tilles noted that the hall does not have enough current to run the new supply with all of the other high current devices in the hall simultaneously. Adding another 1000A supply to the hall would cost about $250K and will not be done. Thus, we will not be able to use the Moeller polarimeter while using the PrimEx dipole.

Mahbub Khandaker

Total Absorbtion Counter (TAC) We have 2 large Pb-glass detectors from Fermilab (20 x 20 x 40 cm^3) Not sure at this point if they are SF5 or TF1. Mahbub will find out. Each block has a single 5" PMT on it Plan to use 1 ADC and 1 TDC channel in DAQ system for this The original concept for the support structure for the TAC is to have it hanging from above with X/Y motion capabilities. It was hoped that this could be installed in April and then raised out of the way of any CLAS target work which is done in the same area. Doug Tilles said there was really no room for the TAC up there while the target is out. By the end of the discussion, it seemed very unlikely that the TAC could be positioned in any permanent location on level2 of the space frame in Hall-B. Given that, it was unclear weather it should be supported from above or below.

Liping Gan

PbWO4 procurement Chinese collaborators have dealt the vendor down to $2.5/cm^3 which is half the price quoted by the Russian source and used in the MRI budget. Chinese collaborators will also contribute about 100 modules Cost in addition to crystals themselves (for shipping etc..) is estimated at about $30/module. Liping thought this might be higher than what we'll really end up paying since that number is based on the fast delivery of PbWO4 modules we got for the recent beam test.