BID™ (Beam Imaging Detector)
Position sensitive MCP detectors for two dimensional
on-line beam diagnostics
High energetic particle or photon beams ionize residual gas. A specially configured imaging MCP-detector can register ions of the residual gas and yield on-line non-destructive 2D beam diagnostics.
On line non-destructive monitoring of geometric parameters and position of beams is a very important task for accelerators and synchrotron radiation (SR) sources.
Del Mar Ventures present BID™ - MCP detectors for on line non-destructive monitoring of the geometric parameters of ionizing beams. A scheme of the BID principle is shown below.
1 - Beam (particles shown by blue points), 2 - Extractor, 3 - Analyzer, 4 - MCP, 5 - Phosphor Screen, 6 - Open Image Intensifier, 7 - Signal for monitoring Beam Intensity
The BID is placed in a beamline with a residual gas pressure of about 10-3 - 10-6 Torr. It registers the products of residual gas ionization by the beam under investigation. The ions created by the beam particles are extracted by an electric field through a narrow slit into an analyzer. The energy of the ions passing through the slit is determined by the electric potential of its origination point. The analyzer is placed at the angle of 45° to the extractor plane and to the direction of the ion drift. This provides a linear correlation between the coordinates of the two-dimensional image and the coordinates of the cross section of the beam under investigation. The X-position in the beam cross section is given by: X1=2*X*Ee/Ea, where Ee and Ea are electric field strengths for extractor and analyzer. As a result, the energy distribution of the ions is transformed into a two-dimensional space distribution on the outer analyzer plane. An Open Image Intensifier based on two Micro Channel Plates (MCP) and phosphor screen forms the image of the real beam cross section. The image is registered by a CCD camera, processed and stored by a computer (not shown in the scheme).
BID™ was successfully tested on beams of charged particles with wide energy and intensity range and on synchrotron radiation beams. Data analysis done by BEAMS™ software provides the cross section distribution of the beam density, beam profiles and the position of the gravity center and its displacement.
For beams with low energy (10 - 100 keV), additional correction electrodes are used to compensate for the shift of the beam under the influence of the detector field.
The spatial resolution of the BID depends on the width of the extractor slit. Depending on the customer´s requirements, the BID may be equipped either with fixed or variable size slit.
For imaging of synchrotron radiation (SR) beams, the BID chamber is filled with Argon or Xenon. This is done in order to increase the BID sensitivity. In this case, the BID chamber has input and output 200 micron Beryllium windows, which are X-ray transparent.
Beam imaging of different particles was done using BID. A list of accelerators and beam parameters is presented in Table 1. The experiments show that we can evaluate the position of the gravity center with an accuracy about 0.1 mm when the size of the beam is about 1 cm.
Table 1.
List of accelerators and beam parameters
Facility |
Institute |
Town, Country |
Particle type |
Energy, MeV |
Sensitivity Threshold, nA/cm2 |
Tandem |
PHEI |
Obninsk, Russia |
O164 |
15 |
1 |
Cyclotron |
RRC KI |
Moscow, Russia |
Li63 |
90 |
5 |
Cyclotron |
RRC KI |
Moscow, Russia |
P |
30 |
10 |
Cyclotron |
Dubna, Russia |
O164 |
200 |
10 |
|
UNILAC |
Darmstadt, Germany |
Se8212 |
360 |
10 |
SR beams imaging was done on the following SR sources:
KSRS (RRC KI, Moscow)
White SR beam with critical energy of 7.5 keV
electron current up to some tens of mA at the energy 2.5 GeV
MAXLAB (Lund, Sweden) MAX-2, (University of Lund)
Monochromatized beam with energy 8.5-13.5 keV and
D
E» 10-3.
In order to get additional information about opportunities to use BID
for your beam imaging needs, please consult our application engineer mcp@sciner.com
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