SPM beam position monitor

Technical Description:

FMB has experience in building blade type X-ray beam position monitors (XBPMs). XBPMs made by FMB are widely used at many synchrotrons to measure the photon beam position at the micron level.

Staggered blade pairs beam position monitors (SPMs) are a type of XBPMs used if only vertical beam positions have to be determined, e.g. at dipole radiation sources. The FMB SPM design is based on a development by HZB (formerly BESSY, see e.g. Peatman, Holldack; J. Synchrotron Rad., Vol. 5 (1998), 639-641).

A typical FMB SPM system consists of the SPM insert, a vacuum chamber, a X-Y-Z manual alignment assembly and a support.

The SPM beam position monitors use four blades, whose narrow fronts are oriented towards the radiation source. They are arranged in two staggered pairs, one pair mounted above the other. With this blade setup the operator is able to scan the off-axis radiation of the source and determine on-line the position of the radiation source centre from the emitted signals.

Size and geometry of the blades will be adapted to the beam characteristics at the place of the position monitor in order to achieve a maximum photocurrent yield at a maximum sensibility.

The blades consist of OFHC copper or Tungsten and will be actively cooled via heat conducting ceramics to resist the thermal load of the radiation source.


Technical Data:

SPM insert     
Type   Staggered blade pairs beam position monitor
Number of blades   4
Blade material   Copper / Tungsten
Aperture / blade opening,   Suggested by FMB,
blade thickness / pair offset   dependent on beam specifications at installation position 
Cooling   Water cooling
Temperature measurement   Thermocouple K-type close to aperture
Electrical strength    500 V
Feedthroughs   Triax, miniature TC flat pin (others on customer request)
Base flange   DN 150 CF fixed
Fiducials   2 / 3 / 4 Hubbs or laser tracker supports at base flange
Pinhole array (optional)   Design according to customer requirements,
0.02 mm min. pinhole diameter dependent on foil thickness
SPM chamber    
Chamber / flange material   1.4301 / 1.4429 (similar 304 / 316LN)
Beam entrance /exit flange   DN 40 CF or different on customer request
SPM insert flange    DN 150 CF fixed, oriented with respect to SPM insert
Additional flanges   Optional on customer request
Column material   Steel (Invar on request)
Fill   Dry sand
Manual chamber alignment   Lateral ± 20 mm, vertical ± 12.5 mm, resolution. (l, v) < 0.1 mm
Alignment via X-Z-stage   Lateral (X) ± 5 mm, vertical (Z) ± 5 mm,
(optional)   repeatability ± 10 µm (± 1 µm with optional encoder)


Datasheet SPM_Beam_Position_Monitor

September 21, 2022
Detectors & Diagnostics
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