Upcoming Review of the Hall D Photon Beam and Tagger Richard Jones, University of Connecticut, for the GlueX collaboration GlueX Collaboration Meeting September , Storrs

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 2 Dates design and simulation position stability specification prototype construction test setup in Hall B alcove results with Hall B photon beam recommendations

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 3 Draft agenda 08:00-09:00 Executive session 09:00-09:15 Charge – 12 GeV team 09:15-09:45 Overview – GlueX 09:45-10:00 Break 10:00-10:20 12 GeV Electron Beam – Accelerator 10:20-10:50 Photon Beam Overview – GlueX 10:50-11:10 Beam Simulations – GlueX 11:10-11:30 Personnel and Machine Safety – 11:30-12:00 Photon Beam Line – GlueX 12:00-13:00 Lunch 13:00-13:15 Tagger Optics – GlueX 13:15-14:00 Magnet Design – GlueX 14:30-15:00 Fixed Array Hodoscope – GlueX 15:30-15:45 Break 15:45-16:15 Microscope – GlueX 16:15-17:00 Diamond Research – GlueX 17:00-17:30Pair spectrometer – GlueX 17:30-18:00 Executive session very squeezed to fit into 1 day

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 4 Overview – 30 minutes Introduction to GlueX Physics justification Justify energy and polarization Overall schedule Budget and manpower

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 5 12 GeV Electron Beam – 20 minutes Overview of accelerator upgrade Progress toward boosting cavity performance Electron beam energy determination 12 GeV beam emittance – and how to know it Beam transport to the tagger hall and optics Interface with tagger – accelerator side Post-tagger beam transport and dump Beam line instrumentation Beam stability and active collimator feedback Expectation for beam halo

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 6 Photon Beam Overview – 30 minutes Systematics of coherent bremsstrahlung Polarization and energy spectra Importance of energy Importance of emittance Machine interface document Requirements for the tagger Requirements for the pair spectrometer Requirements for the collimation system

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 7 Beam Simulations – 20 minutes Tagger area: – background count rate in focal plane counters – specification on electron beam halo – scattering at beam exit from tagger vacuum chamber – background from dump Cave extension area: – active collimator design and performance – shielding optimization in the collimator cave – backgrounds in the pair spectrometer – background in core of photon beam, impact on GlueX

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 8 Photon Beam Line – 30 minutes Layout of equipment in tagger hall – vacuum system – 3D model – instrumentation – alignment – installation – cost+schedule Layout of collimator cave – shielding issues – 3D model – installation plan – alignment – cost + schedule

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 9 Tagger Optics – 15 minutes Opera model Ray tracing results Optimal location for tagging counters Quadrupole and vertical focusing

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 10 Tagger Magnet Design – 45 minutes Change to one magnet design Layout and assembly of magnet and vacuum system Alignment plan Force calculations deflections tolerances Review of specs and drawings Instrumentation Power supply Mapping Schedule

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 11 Fixed Array Tagger Hodoscope – 15 minutes Coverage and segmentation Readout, resolution and rates Crystal alignment considerations End-point tagging Support structure and alignment

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 12 Tagger Microscope – 30 minutes Coverage and segmentation Scintillating fiber geometry Readout, resolution and rates Vertical readout and collimation Tagging efficiency and backgrounds Support structure and alignment

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 13 Diamond Research – 45 minutes Thickness criteria: performance vs. lifetime Diamond assessment with X-rays Challenge of producing 20 micron radiators Assessment with X-rays Development plan

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 14 Pair Spectrometer Design – 30 minutes Specification Choice of magnet Design of vacuum system and shielding Counter segmentation and resolution Rates and background

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 15 Recommendations from 2006 review 1.The Collaboration should work closely with the 12 GeV Accelerator Project Team to insure that the electron beam emittance, positioning, stability, and halo match the requirements of the experiment 2.The Collaboration should revisit the time resolution requirement for the tagger hodoscope system to optimize the rejection of accidental coincidences (σ ≤200 ps seems to be a reasonable goal). 3.Complete the Monte Carlo simulation of the background in the tagging counters caused by backscattering from the dump or the beam line 3.Complete the Monte Carlo simulation of the background in the tagging counters caused by backscattering from the dump or the beam line. 4.Consider a clamped Al foil with an O-ring seal for the vacuum chamber exit window. 5.To enable an online monitoring of the vertical electron distribution in the focal plane, the count rate distribution of (at least some of) the microscope detectors outside of the mid-plane should be read out, too.

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 16 Recommendations from 2006 review 6.Include the energy calibration of the tagging system in the commissioning plan. 7.Include as an option in the procurement strategy the possibility that different manufacturers produce the tagging spectrometer components, and that these components are assembled at JLab for the first time. 8.The Collaboration should work closely with the 12 GeV Civil Construction Project Team to make sure that the tagger area dimensions and the access to the area are consistent with the planned assembly and alignment strategy for the tagging system components. 9.Contact rigging and alignment services at JLab to make sure that the planned assembly and alignment strategy for the tagging system is feasible and consistent with the best practices of those groups. 10.The possibility that the system will have to be disassembled should be included in the design studies.

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 17 Issues to resolve before review Pair spectrometer – energy calibration precision, absolute accuracy – polarimetry precision from spectral analysis Active beam position stabilization plan – conceptual design that accel. group agrees with Passive collimators design optimization – replace outer layers with lead, test with simulation Redo tagger background studies – get revised halo model from CASA – redo the background simulation – cpu intensive!

GlueX Collaboration Meeting, September 18-20, 2008, Storrs 18 Issues to resolve before review Flesh out plan for diamond development – vendors with thinning capability – manpower Assemble pre-brief materials Assign and write talks