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Wedge Plates or Crotch Absorber

Crotch Absorber







Straight Chamber with Crotch-Absorber.

SLS Vacuum system

Crotch-Absorber Figure

Crotch-Absorber Figure

Technische Beschreibung

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.

Technische Daten

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

Figure 2

Splitted Crotch Absorber

Figure 3

Straight Vacuum Chamber Riva- CGM2
incl. two absorbers (PSI – SLS)

Download this file (Crotch-Absorber_Version2.pdf)Wedge Plates or Crotch Absorber