F.Brinker, DESY, July 17 st 2008 Injection to Doris and Petra Fitting the detector in the IP-region Radiation issues Beam optic, Target cell Polarisation Work laying ahead Operational constrains Summary

Injection for DORIS III and PETRA III Mode 1 (e+) : DORIS needs new injection every 8 hours PETRA runs in top up mode – one new bunch every 1-30 seconds, depending on current and lifetime Mode 2 (e- or e+): DORIS and PETRA are running in top-up mode 1 bunch to PETRA every 1-30 sec 1 bunch to DORIS every sec 450 MeV Linac: Gun delivers electrons, which can be converted to positrons after half of the linac PIA : accumulation of several linac pulses to increase the bunch current DESY : 12.5 Hz / 7 GeV Synchrotron – a trigger generator allows the extraction at different energies to either Doris or Petra

Geometry of the detector and the IP-region

Top view with radiation shielding

View to the IP-region from outside with ARGUS on the left side

Radiation issues: No of particles lost in 30 days at a lifetime of 0.6 h and a maximum current of 140 mA: ~ 5 E14 The dominant loss process is energy loss by bremsstrahlung – the particles would be lost mostly in the arc following the target and at the typical aperture limitations (Harwi, BW1, Septum) Particles lost in normal synchrotron radiation mode: between 3.3 E14 and 5.9 E14 per year ( ) → Radiation dose per year would be doubled Radiation shielding is sufficient Radiation level at HASYLAB with open beam shutters too high ( from measurements when we had a small vacuum leak ) – but the level should be fine when the shutters are closed A significant part would be lost at the wiggler chambers → to protect the permanent magnet material the wiggler gaps should be open and some wigglers have to be moved away from the beam pipe (1-2 days)

New optic with a reduced beam size at the IP : from σ x x σ z = 3.7 x 0.7 mm 2 to 1.1 x 0.3 mm 2 Due to the asymmetry of the detector the target cell is not at the IP but at about 0.75 m Optical functions at the insertion devices and injection are kept nearly unchanged

Target cell To reach a high gas density the target cell conductivity should be as small as possible The conductivity is proportional to the cross section divided by the inner surface of the tube Making the target cell the most stringent aperture limitation in the ring would probably cause background problems and could reduce the beam lifetime Present aperture limitations: –Wiggler BW1, β Z =6.7m, vertikal full aperture = 11mm –Absorber for Harwi, β X =15.5m, horizontal full aperture = 60mm Corresponding target cell dimensions: 28 x 7 mm 2 I would suggest an elliptical chamber of 30 x 8 mm 2 The conductance would be 75% of that of the present 15mm diameter circular pipe

Polarisation For the case that a beam polarisation could influence the cross sections M. Vogt and D. Barber calculated the expected polarisation at the energies of interest Of course the polarisation would be almost completely transversal! At 2.3 GeV: Rise time about 2.5 h and polarisation up to 90% shown are results for 10 seeds with a typical orbit distortion

6 min. rise time at 4.5 GeV 40 min. rise time at 3.1 GeV

View to the IP – the cavities has to be moved to SL 26m

Moving the cavities Present situation Changes for Olympus operation The 2 cavities would be moved to SL 26m The waveguide distribution would be changed such that 4 neighbouring cavities can still be connected to one RF-station – one waveguide passing Olympus Controls, interlocks etc. have to be changed accordingly the costs would be about 10 k€

Magnet power supplies 1 additional power supply is needed for the extra pair of quadrupoles –a device from Hera-p could be used here Most of the P.S. have to be modified to allow the polarity switching: –24 switches for 400 A : 60 k€ –10 switches for 800 A : 40 k€ –Mechanics, cabling and controls : 70 k€ → 170 k€

Injection elements Also the kicker pulses have to reverted Since the high voltage connections with well defined inductance can’t simply be switched, new pulsers would be needed which can change the polarity of the current pulse There are two kickers at DORIS and one at DESY The material costs per pulser including the HV power supply are 29 k€

Vacuum elements Valves to separate the IP-region from the rest of the ring Collimator insertions – have to be specified Intersections to connect the ring vacuum with the experiment vacuum system

Tasks for installing the detector :

Operational issues e + /e - operation of LINAC, PIA and DESY is possible – switching takes about 5 min. ( … on the long term DORIS and Petra should run with electrons only ) For a fast change of the polarity of the DORIS magnets additional power supply switches have to be installed. The change of the particle type in DORIS should be possible within one hour. Due to the lifetime reduction, energy changes and increased radiation a parallel operation with Hasylab is not possible. Due to the frequent changes of the particle type also a common operation with Petra III is excluded ( at least for the normal Top-up mode at Petra! ) The particle optic in DORIS is matched to keep the optical functions nearly unchanged at all wiggler positions – therefore it has not to be changed for the synchrotron radiation runs. The target cell can stay in the ring.

Summary The space for a detector like Blast is still available Some modifications (and investments) are necessary – but no “show-stoppers” are visible An optic has been developed which should work for synchrotron radiation runs as well as high energy runs The most time consuming work can be done outside the Doris tunnel and needs no shutdown time