Wedge Plates or Crotch Absorber

Technical Description:

Wedge plates absorbers (also referred to as Crotch absorbers) are absorbers predominantly inserted in the crotch part of a dipole chamber. They are suitable for wide flat shaped photon beams with high total powers as well as for high power densities.
A wedge plates absorber consists of two separate plates fixed in a base flange. Each plate has a number of parallel wedges with intermediate grooves on the absorbing side. The wedges of each plate fit the grooves of the other plate without contact. The plates can expand under heat load with moderate stress generation (S. Hermle et al; Proceedings of PAC 1999, New York, p.1360-1362). For radiation the gap between the plates is fully closed apart from the customer specified aperture(s).
Size and geometry of the plates will be adapted to the beam characteristics at the place of the absorber in order to achieve safe absorption.
The plates are made of a copper material and can be water-cooled independently or in-line to resist the thermal load of the radiation source.

Technical Data:

Type:   Wedge plates absorber insert
Number of plates:   2
Plate material:   OFHC-Copper / Glidcop on request
Plate design and dimensions:   Suggested by FMB,
dependent on beam specifications at installation position
Number. of apertures /
aperture dimensions:
  As specified by customer

Maximum absorbed power /
thermal power density:
  5 kW and more, dependent on space available at
installation position / up to 50 W/mm² (with Glidcop,
Cooling:   Water cooling
Cooling scheme:   Plates independent or in-line by outer connection
Base flange:   DN 63/100/150 CF fixed  (others on customer request)
Flange material:   1.4429 (similar 316LN)  (others on customer request)
FEA calculation:   FEA calculation report for thermal and stress analysis
Temperature measurement:

  1 / 2 thermocouple K-type in plate(s),
Feedthrough miniature TC flat pin
(others on customer request)
Manual aligner (optional):

  Manual absorber alignment;
normal to port ± 3 mm (resolution < 0.1 mm), tilt ± 2 deg



Figure 1

Photon Absorber in a Quadrupole Chamber
  crotch absorber figure 1 0005
Figure 2

Splitted Crotch Absorber
  crotch absorber figure 2 0006
Figure 3

Straight Vacuum Chamber Riva- CGM2
incl. two absorbers (PSI – SLS)
  crotch absorber 001 sls vacuum system 0001


 Datasheet Crotch-Absorber

September 9, 2022
Storage Ring Components
We use cookies

We use cookies on our website. Some of them are essential for the operation of the site, while others help us to improve this site and the user experience (tracking cookies). You can decide for yourself whether you want to allow cookies or not. Please note that if you reject them, you may not be able to use all the functionalities of the site.