Absorbers

The Absorber serves to absorb the synchrotron radiation and to carry away the related heat capacity of the absorber body by way of water cooling.

The absorber insert consists of

the basic flange (DN 100 CF),
the absorber body,
in standard design made of OFHC copper or Glidcop®,
an OFHC copper coil (6 x 1) vacuum-brazed to the back and serving as water cooling,
-a bar-like support assembly which is atmospherically sealed using a membrane bellows, and
-a pneumatic cylinder equipped with 2 proximity switches used as end switches.

The pneumatic cylinder is double-acting. In case of a loss of media (compressed air, voltage) the absorber moves into the beam path.
The electrical proximity switches can be exchanged against mechanical micro switches.
The positioning and arrangement of the intensity absorber in the front end is made together with a 150l/s ion pump, the all-metal gate valve, a fast-closing valve and a small chamber on a separate steel column with an x, y, z adjusting frame.

Technical Datas

Overall dimensions -Base flange: -Height:	CF 100 ( bigger O.R. ) about 750 mm
Active length in beam direction:	appr. 80 mm
Aperture:	appr. 20 x 10 mm²
Heat load:	appr. 4 kW
Absorber material:	OFHC-Copper or Glidcop^®
Absorber stroke:	50 mm
Cooling water connection:	Swagelok
Cooling water pipe:	tube 6x1, copper
Leakage rate:	<1 x 10^-10mbar • l • s^-1
Compressed air:	6 bar

Radiation Absorber

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Radiation Absorber

Crotch or Photon Absorber

Technical Description

This kind of absorber is located in the crotch part of the dipole chambers. It absorbs a part of the synchrotron radiation power density by about 50W/mm2
(Remark: This value permits the use of OFHC copper as absorber material).
The absorbers for the synchrotron radiation can be also made of GlidCop^® (for higher density). The Photon or Crotch Absorber has a direct water cooling system. They are fitted into an orifice which is connected with the keyhole of the vacuum chamber (see reverse side - figure 1). An ion pump is connected directly under or beside the absorber on the same orifice.
The Cooling is done by four pin holes with a 6x0,5 mm tube for the incoming water. A wire is wound around the inner tube in order to enhance the heat transfer. The water velocity is 3m/l.
The cyclic temperature changes and the corresponding strains lead to fatigue of the material which can lead to failure. In order to reduce the strain the absorber is split into two halves with a comb like structure each with two cooling channels (see reverse side - figure 2). The comb structure of the upper and the lower part fit together with 1 mm separation. Due to an angle between the synchrotron radiation and the normal of the absorber no radiation can pass the absorber. Since the synchrotron radiation now hits alternating small sections of the upper or lower part of the absorber which are slightly separated, the hot sections can expand slightly and thus the maximum stress is reduced [1].

FMB produces two modifications of Crotch Absorber:
- Fixed Absorber (see reverse side - figure 3, the left one),
- Adjustable Absorber (see reverse side - figure 3, the right one).

References
[1] S.Hermle, D.Eilenfeld, E.Huttel, E.Wiedemann,
“Layout of the Absorbers for the Synchrotron Light Source ANKA”, PAC 1999, New York

Figures

Figure 1 Photon Absorber in a Quadrupole Chamber (PSI – SLS)
Figure 2 Splitted Crotch Absorber
Figure 3 Straight Vacuum Chamber Riva- CGM2 incl. two absorbers (PSI – SLS)

Intensity Absorber - Photon Shutter

Intensity Absorber - Photon Shutter

Intensity Absorber - Photon Shutter

Radiation Absorber

Radiationabsorber

Radiationabsorber

Radiationabsorber

Radiationabsorber

Radiationabsorber

Radiationabsorber

Radiationabsorber

Wedge Plates or Crotch Absorber

Crotch Absorber

Crotch-Absorber

Crotch-Absorber

Crotch-Absorber

Crotch-Absorber Figure

Crotch-Absorber Figure

Intensity Absorber - Photon Shutter

Technical Description

Technical Datas

Radiation Absorber

Crotch or Photon Absorber

Technical Description

Figures