DORIS storage ring

September 15th 2009 Olympus technical review at DESY, F.Brinker 1

DORIS storage ring

•Olympus in the IP-region

•Beam optic, changes on the lattice

•Beam dimensions, Target cell

•Synchrotron Radiation

•Beam acceleration, Particle polarity

•Machine studies


Geometry of the detector and the IP-region


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


Top view with radiation shielding


Straight section from the arc to the IP

Vertical scraper

Horizontal scraper

Main source of synchrotron

radiation

beam direction


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


Energy [GeV] 2.0 2.3 4.5

Max Beam Current [mA] 140

Target cell 27 mm x 9 mm

Beta-x IP < 2.7 m

Beta-z IP < 1.5 m

Lifetime ≈ 0.7 h

Energy acceptance > 0.8%

hor. Emittance [nm] 91 119 440

hor. Dispersion at IP [m] -0.5

hor. beamsize (1) at Target[mm] 0.55 0.63 1.2

vert. Emittance (5% coupl.) [nm] 4.5 6.0 22

vert. beamsize (1) at Target[mm] 0.09 0.11 0.21

energy spread (1) [%] 0.049 0.056 0.11

hor. damping time [ms] 29.0 19.1 2.6

vert. damping time [ms] 27.6 18.1 2.5

long. damping time [ms] 13.5 8.8 1.2

Main

Parameter


Horizontal Acceptance and Beam sizes at 4.5 and 2.3 GeV

The acceptance is defined by the existing aperture limitations and limits the extend of any beam halo

0

10

20

30

40

50

60

70

80

90

-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15

position from IP [m]

[mm

]

Acceptance 20 sigma(4.5 GeV) 20 sigma (2.3 GeV)


vertical Acceptance and Beam sizes at 4.5 and 2.3 GeV

0

5

10

15

20

25

-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15

position from IP [m]

z [m

m]

Acceptance 20 sigma(4.5 GeV) 20 sigma (2.3 GeV)


Vacuum system

current position

to be removed

new position

current position

new position

valves

Adapter chambers


Synchrotron Radiation [B.Nagorny, A.Schmidt]

Energy [GeV] 2.0 4.45

Power through Target [W] 1.1 23.9

Photons through target [1/sec] 1.4E16 3.0E16

Power on fixed collimator [W] 3.4 76.4

Photon on fixed collimator [1/sec] 4.4E16 9.7E16

Critical energy [keV] 1.56 16.0

About 60% of this could be shielded by the movable scaper stations


0

10

20

30

40

50

60

-0.08-0.06-0.04-0.02 0 0.02 0.04 0.06 0.08

-0.04

-0.02

0

0.02

0.04

0 10 20 30 40 50 60

Synchrotron radiation at 4.5 GeV - dipole

W/cm²

Linear power density: 24 W/cm

0 2 4 6 8 -8 -6 -4 -2

4

2

0

-2

-4

x [cm]

y [cm]


Injection for DORIS III and PETRA III

For OLYMPUS particle beams with electrons and positrons are needed with energies of 2.0 to 2.3 GeV

The Linac, PIA and DESY are able to deliver both particles.

The energy of the DESY synchrotron varies sinusoidal with a maximum energy of up to 7 GeV

The extraction energy is defined by the peak energy and the timing of the extraction within the energy cycle. Both are variable.

Modifications are needed for fast switching of the magnet polarity of DORIS and the transport.

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


Machine studies on February 7th •Injection into 10 bunches

•Final current 170 mA after 6 minutes

•Varying efficiency – probably due to effects at DESY:

•DESY operated at normal maximum energy of 4.5 GeV

•At 2.3 GeV the beam is not fully damped to its equilibrium emittance

•Possibly beam blow up due to resonances


Machine studies on February 7th

Stored beam with good conditions:

• I = 150 mA• Lifetime = 8.5 hours

Not so nice:

Longitudinal beam excitation (oscillation with ~1cm Amplitude)

Limits lifetime at higher currents

maybe increased particle background


Machine shift Aug. 3rd

Beam intensity limited to 120 mA in 10 Bunches , long. stable


Machine shift Sept. 9th

90%+ injection efficiency , 30 mA injected in 2 min.


Sept. 9th, horizontal scraper measurements

2.3GeV, Lifetime dependance on scraper position

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 100 200 300 400 500

scraper position x^2 [mm^2]

log

(L

ife

tim

e[h

])

beam core - gaussian

profile

region of beam halo

halo ends at≈ 19mm

since the horizontal beam size at the IP is about a factor 2 smaller, the beam halo would extend to ± 10 mm from beam center

results are preliminary, the scraper position has to be verified!


2.3 GeV, Lifetime dependence on vert. scaper position

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 10 20 30 40 50

scraper position z^2 [mm^2]

log

( l

ife

tim

e[h

] )

Sept. 9th, horizontal scraper measurements

beam core - gaussian

profile

region of beam halo

halo ends at≈ 5.5 mm

since the vertical beam size at the IP is about a factor 3 smaller, the beam halo would extend to ± 1.8 mm from beam center

results are preliminary, the scraper position has to be verified!


topics for further studies:

• stabilize ejection from synchrotron / improve transfer efficiency

• find optimal working point for tunes

• experiences with second long. feedback amplifier (installation at end of September)

• investigate max. stable beam current (presently 120mA)

• tests at 2.0 GeV


Infrastructure

•Detector power supply

•Detector cooling

•Polarity switches

•Kicker pulser

•Preparation of the experimental hall

•Modification of the IP region

•Installation of Olympus


Detector power supply

• A 10kV to 480V transformer is available and will be placed outside the experimental hall

• The foundation has to be prepared• The 7000 A power supply from Petra has to be installed

in the hall • The cabling to the transformer (10kV), to the power

supply (2500A, 480V DC) and to the detector (7000A, 225V DC) has to be done mainly by an external company


Water cooling of toroid• The capacity of the cooling tower is sufficient• The cooling water circuit to ARGUS is still available• It’s now in use for the cooling of transport line magnets• The capacity of the circuit is sufficient for Olympus after

smaller modifications ( 20 m of new tubes with larger cross section )

• The two installed pumps have to run in parallel • The pressure has to be reduced from 12 bar to 5 bar

Cooling for the moved cavities is still available, the last few meters are missing

Cold water for air conditioning is also available, tubes have to be laid


Trans-former

Water cooling

Power-supply

Electronics hutch


Polarity switches• There are 46 main magnet power supplies at DORIS and

the transport line• 12 of those are already replaced by bipolar devices• 10 devices with currents below 270A can be modified

with polarity switches from HERA• The remaining 24 devices need new polarity switches,

14 devices for 400A and 10 devices for 800A• Cabinets, controls and cabling have to be done


Kicker pulser

• The extraction/injection elements at DESY and DORIS have to be bipolar

• The Septa can be modified accordingly• The Kicker ( 2 DORIS + 1 DESY ) need new power

supplies and new pulsers which would be build at DESY


Preparation of the experimental hall

• Part of the hall is in use for an DESY exhibition, these objects will be removed and partly find a new home in HERA hall west

• The ARGUS detector will be disassembled and removed

This work will start soon and should be finished by the end of this year


Modification RF-lab

• An RF laboratory for testing of Tesla cavities is placed on the outside of the DORIS ring

• A rectangular region of 2.5 x 9.5 m has to be cut out – Install dust cover– Remove walls – Cut ceiling and floor– Build new walls– Change installations ( crane, electricity, water etc.)

This work can start in summer 2010, when the ongoing work in the laboratory is finished (earlier, if possible)


Modification of the IP region (1. shut down in winter 2010/11)

• Move signal cables from IP region ( can be done in advance )

• Remove interlock installations• Remove shielding blocks• Remove accelerator components

– Cavities, vacuum chambers– 4 quadrupoles– Girders

• Install dust cover• Demolition work on parts of concrete


Modification of the IP region, cont.

• Build up new shielding• Install new girders/support for experiment vacuum• Put in 6 new quadrupoles• Install vacuum system, including target chamber and

new vacuum valves• Install cavities at the new position• Cabling, water connections• Install modified interlock system• Surveying


Installation of Olympus ( 2. shut down in summer 2011 )

• Remove part of shielding• Remove vacuum system between valves• Roll in the detector• Install vacuum chambers• Connect cooling water and electrical power• Rebuild shielding• Surveying• Interlock tests


Summary• The space for the detector is still available• Some modifications to the storage ring are necessary – but no

“show-stoppers” are visible• A beam optic has been developed which should work for

synchrotron radiation runs as well as for OLYMPUS• The most time consuming work takes place outside the Doris tunnel

and needs no shutdown time• The modifications of the IP region can be done within 2 shutdown

periods• The infrastructure for the experiment can be provided to a large

extend with available equipement

The effort to realize the experiment is significant, but it’s only a small fraction of what’s already available.

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DORIS storage ring