This background information is meant to supply information on detector issues and progress since November 2002 when the latest version (4) of the GlueX/Hall D Design Report was issued.
This review of the GlueX detector is being conducted as the collaboration prepares for a 'Lehman-type' Review as part of Critical Decision 1 (CD1) approval. The GlueX physics and detector are described in version-4 of the GlueX/Hall D Design Report. The entire Design Report can be downloaded, and in particular the tagger spectrometer and detector are described in Chapter 4 (Photon Beam) and Chapter 6 (The GlueX Detector in Hall D).
GlueX/Hall D and the Jefferson Lab 12 GeV Upgrade, of which it is a subset, received CD-0 approval from the Department of Energy on April 19. Based on this milestone, the project expects to face a CD-1 review in the summer of 2005. This is an appropriate time to review the present statuts of the detector design and R&D and focus on issues which are required for further approval. We conducted a review of our electronics in August of 2003.
Although the GlueX detector will be state-of-the-art it does not push the envolope compared to experiments already taking data or planned for the near future. The channel count is modest (approximately 20k channels for fast control and 10k for slow). The events are relatively simple (about 5kB/event) with an average of about five charged particles and two to four photons per event. The data rates are also modest (about 400kHz for the total hadronic rate). At the highest beam flux of 10^8 photons/s the archived data rate will be 100 mB/s. Pipelining will be built into the entire trigger, digitizer and data acquisition systems at the outset. This will allow seamless upgrades from initial photon fluxes of 10^7 photons/s up to the design goal of 10^8/s.
Event reconstruction will also be straightforward and we expect to exploit Grid architectural tools that will be in place by that time. The challenge unique to GlueX will be developing the phenomenological and software tools needed to do the amplitude analysis required for identifying meson quantum numbers.
Radiation effects are also not an issue. They will be lower than those experienced by the CLAS detector in Hall B at Jefferson Lab which has been in operation now for several years. Background sudies for GlueX have been made.
The major detector subsystems are the following:
This is an appropriate time to review whether the detector design matches the requirements of the experiment; the technologies chosen are appropriate to the task; the plan for installation parts avoids interference between subsystems; and are the tasks matched to the manpower and expertise in the collaboration.