F.Brinker, DESY, July 17st 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 30-60 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 (2003-2007)

• → 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)

doct3w doct3wBlast (symm.point / at 1.2 m) Emittance at 4.5 GeV 465 nm 438 nm Qx 7.17 7.17 Qz 4.77 5.23 βx 26 m 2.4 m 3.2 m βz 9.7 m 1.5 m 2.6 m Dx -1.3 m -0.5 m

Blast IP Additional quad at ± 7m

New optic with a reduced beam size at the IP :

from σx x σz = 3.7 x 0.7 mm2 to 1.1 x 0.3 mm2

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, βZ=6.7m, vertikal full aperture = 11mm– Absorber for Harwi, βX=15.5m, horizontal full aperture = 60mm

• Corresponding target cell dimensions: 28 x 7 mm2

• I would suggest an elliptical chamber of 30 x 8 mm2

• 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

Topic DORIS shutdown Necessary ?

Components to buy

Remove Argus No - Revise/rebuild rails and container No ? Install Blast No Electric power for detector No Low voltage distribution

(230V/50Hz ?) cables to power supply (reuse PS from Petra)

Water cooling of detector No Water pumps Cooling pipes

Air conditioning No Air conditioning design of collimator system Construction of vacuum parts No - Move cavities from IP to SL 26m Yes Pipes, cables Modification of vacuum system Yes 2 valves

collimator insertions Modification of magnet girder Yes - Installation of 2 Quadrupoles Yes cables Installation of PS polarity switches Yes Remotely controlled polarity

switches, cables, controller relocate cables and water pipes from IP Yes Pipes, cables Remove concrete blocks from IP-region Yes - modify workshop on the outside of DORIS Yes ? Shift detector in the ring Yes - Build up radiation shielding Yes ? Safety ( interlock, emergency stop, fire detector, gas detector )

Yes Detectors, cables, interfaces

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