First Operational Experience with DORIS II
DORIS II is a completely new designed e+-e- storage ring with a mini-beta scheme. After first runs with a 8 cm optic, the vertical amplitude functions in the interaction points were reduced to 4 cm. This yielded luminosities of L = 1.5 . l031 cm-2sec-1 with 2 × 27 mA at E = 5 GeV. Because of the short injection time, an integrated luminosity of more than 600 nb-1 per day has been obtained.
Luminosity enhancements at SLAC
The hiARK III detector is shown in Figs. l(a) and l(b). The detector is described in Ref. 1 and its main subsystems are described in Refs. 2-6. Briefly, working out from the interaction point, the detector consists of an inner trigger chamber, followed by a large drift chamber, a time-of-flight (TOF) counter system, a gas sampling cylindrical shower counter, a solenoidal coil which generates an axial magnetic field whose value at the interaction point is four kilogauss, the magnet flux-return steel, and finally a muon counter system. Gas sampling endcap shower counters mounted on the removable steel doors complete the detector. The novel feature of the detector is the cylindrical shower counter, which is placed inside the solenoidal coil and has a high detection efficiency for photons with energies as low as 50 MeV.
rPET detectors design and data processing
Small animal PET systems based on rotating planar detectors posses some interesting advantages for high sensitivity, high resolution imaging. We have designed the rPET detectors based on MLS crystals assembled on a 30times30 matrix optically coupled to a flat-panel PS-PMT. Weighted position readout circuits pre-process the 64 signals from the 8times8 anodes matrix, which are digitized using a charge-integrating converter. The amplification electronics, including the trigger output for coincidence detection, and the high voltage supply are integrated in a three PCBs stack that forms the base attached to the back of the PMT. The whole assembly is enclosed in a light tight, lead (Pb) shielded aluminum box. The detectors are mounted on a rotating gantry with more than 180 degrees rotation span. The digitized events are screened and histogramed, and a modified center of gravity algorithm removes from the position calculation those signals with poor signal to noise ratio. Apparent mean crystal size on the 511 keV field-flood images is 0.6 mm, mean peak-to-valley ratio is better than 8, and intrinsic resolution is 1.5 mm at the central row, with the energy window wide open. Sensitivity (CPS) for a pair of these detectors set in coincidence at 160 mm distance is 1%