Meeting solid ec 2013 01 22

Meeting call in instruction (valid through July 16): US 866-740-1260 International 303-248-0285 Access code: 8206694

Meeting room: F224/225 except Jan. 29 which will be in F226.

Compiled todo/summary list of EC meetings, 2013/1/4-2013/1/22:

1. Preshower design:
   • Now we will focus on using "fan"-shape Preshowers. We will build one for the large angle, and one for the forward angle that will be the same for PVDIS and SIDIS. We will start from 30 segments, but more segments might be necessary depending on what the simulation shows. The LA PS will consists of one Pb layer followed by one Scintillator layer, and the FA PS will have two Scintillators sandwiching one Pb layer.
   • The readout will be the same as before: We will imbed WLS fibers in the scintillator pads, then connect them to clear fibers for going outside the fields, and then connect to PMTs, although some readout R&D is still in the plan (see below);
   • To do:
     1. Jin Huang: Determine the effect of using larger "fan" size and the number of segmentations, thickness Scintillator layers (10cm or 20cm for the post-Pb layer? What should be the thickness of the photon-rejection scintillator layer?). For the LA PS this will depend on 1) PID; 2) capacity of the PMT; and 3) S/N ratio; and for the FA PS this will depend on 1) PID; 2) capacity of the PMT; 3) S/N ratio; and 4) How much photon suppression we can get.
        • 2013/2/5 update: Jin finished preliminary simulation on the photon rejection, see [| his report]. The photon rejection is 7:1 for 1-7 GeV/c or 1:20 for 1-2 GeV/c, if cutting on 0.5MeV below the MIP. Jianping questioned more on the background problem which may force the raising of the cut.
2. Readout options to dos:
   1. Zhiwen Zhao: with the new, larger fan-size, how many WLS fibers do we need per "fan pad" and how to arrange them?
   2. Zhiwen Zhao: Will using field-resistant PMTs (like the one in Cherenkov) an option for FA PS? This will depend on a) the cost saved on WLS and clear fibers as well as machining the scintillator pads; and b) the cost of field-resistant PMTs ($3k each for 2" PMTs - per Jin and Yi); If PMT-directly-readout is an option then possible lightguides should be looked into.
      • On 2013/1/15 JP asked why Cherenkov is not using fine-mesh PMTs.
      • 2013/1/15 meeting update: fine-mesh PMT has no obvious gain loss up to 1500 Gauss; price about $1500 with standard glass for 2in diameter. Gain is about 5E5, good enough for our EC. The other option is a segmentable "multi-anode" (into 4 channels) $5k PMT but is less field resistant, but >10 in gain.
      • 2013/1/22 update:
        1. Zhiwen commented that Cherenkov is using multi-anode rather than fine-mesh PMTs is purely due to geometric reasons. Multi-anode PMTs match better with their signal output.
        2. At the moment both multi-anode and fine-mesh PMTs are still possible options for EC. To do for Zhiwen: study/compare their
           1. field resistance
           2. gain, also gain loss due to field
           3. max current capacity
           4. cost, including cost comparison with WLS-clear fiber readout. 50-mm square multi-anode cost $5000 each;
           5. JP questioned why we don't consider cheaper PMTs, if field only reduce the gain by "some factor", since our need for gain isn't as demanding as Cherenkov;
3. Support structure:
   • Argonne engineers will work on this with inputs from Zhiwen. Many other people will be kept in the loop.
   • Jin commented that we do not need to have the Preshower made at IHEP anymore.
   • To do by Zhiwen: In our latest email with Argonne engineers we should give the flexibility of using W or Pb with Al frame for the Preshower, but we should reject stainless steel due to possible magnetism and Cu or Al alone (due to lightness). <- emailed 1/8
   • Update 2013/1/15 Zhiwen said Argonne engineers already have some preliminary design;
   • Hexagon shape (suggested by Argonne engineers) is still an option depending on if the support is easier to design.
4. Super BigBite test with HERA modules:
   • Mark Jones has 10 HERA-B modules with size 11x11 cm^2, about 20 X0 long, but much thicker layers. Exact sampling and total thickness to be confirmed. Bench test of modules being setup now.
   • HERA-B has a total of 500 middle and 1700 outer modules

(see [| their NIM paper]). (Zhiwen) inner modules had 4 readout, outer modules had 1 readout.

1. • If energy resolution and pion rejection are close to what we need, could consider using these modules for both SBB and SOLID.
   • Todo for Zhiwen/Jin: Need simulation to: 1) Find out what expected performance of HERA modules is; and 2) compare with bench test to see how good our simulation is.
     • Update 2013/1/31: Jin did simulation for HERA modules, see [| his report]
   • Beam test is being considered at the Fermilab electron beam test facility. JP suggested SLAC might also have some test facility.
2. Communication with IHEP:
   • We received reply from Vladimir on the new Preshower design, however he asked for detailed design diagram for further discussion. We don't have such design yet. For fiber connectors he also asked for a design, Zhiwen has asked Leoni Fiber to see if they already have something.