Revision as of 09:23, 11 June 2008

Outline for Bcal using existing technologies

• Readout of the barrel calorimeter based on conventional photomultiplier tubes (GlueX-doc-832, Jun 2007)
• Issues that need to be considered (rough outline)
  1. light guides and collection
     • fiber light guides? re-evaluation of the granularity for the inner cal
  2. light detector
     • planacons, wire mesh pmts
  3. magnetic fringe fields / shielding
     • Preliminary field calculations using ANSYS available
  4. cabling / number and sizes of cables / signal degradation
     • cable differences between various detectors, e.g. HV
  5. dark box / "wrapping of detector"
     • presently no scheme has been worked out for any scenario
  6. impact on photon reconstruction [what is our current geometry?]
     • what material is included for the WCs/SiPMs/cables?
  7. cost estimates
• Comments:
  • Area of fibers cover 50% of the area of the end of the Bcal. Reduction is 2.
  • Area of the output of the WC (1.2 cm2) reduces the readout by 4cm2/1.2cm2 = 3.3.

Space Constraints

• The Sketch below is to illustrate the space constraints for any light collection and readout system. We note that this is the geometry that has been presented at reviews; the 'current geometry' given below has a somewhat different description:

Current Geometry

The current geometry as visualized by ROOT (courtesy of Beni) is given below. All guides (both inner and outer) are represented by brown trapezoids (simple representation of a Winston Cone). The outer 'WC' are 10 cm long. The inner 'WC' are 5 cm long. The inner 'WC' are followed by 2x2x2 cm3 gray Al block to represent the SiPM. Six 'SiPMs' are butted and appear as a single radial piece connecting the 'WC's. Cables are simulated with material (not shown) that is routed quickly out and around the yoke. The Al plate (also gray) extends beyond the end of the Bcal (likely unchanged from previous longer Bcal geometry so should be updated).

Cathode coverage using fine-mesh pmts

Nominal design

         full area     Detectors           cathode   Fraction
inner     111.6 cm2    24 SiPM 1.44cm2     34.6 cm2   0.31
outer     113.4 cm2    4 XP2262 D=4.4cm    60.8 cm2   0.53


Fine-mesh pmts Option.
Note: Nine of the smallest 1" pmts bearly fit with housing over the inner
face. Four 1.5" pmts can fit over the outer face.

         full area     Detectors             cathode   Fraction
inner     111.6 cm2    9 H6152-70 D=1.75cm   21.6 cm2   0.19
outer     113.4 cm2    4 H8409-70 D=2.7cm    22.9 cm2   0.20

Layout