Beam Tomography Beam Tomography

Maximum Entropy
Beam Tomography

Beam Tomography Beam Tomography
Beam Tomography for non-destructive Projected Emittance Measurements

Beam Tomography The Maximum Entropy Tomography (MENT) program has been developed by Gerald Minerbo at the Los Alamos Scientific Laboratory in New Mexico (USA) [1] and some time later successfully applied to Beam Tomography by scientists at the same laboratory [2]. This Beam Tomography Program is coded in FORTRAN-77 with the exception of the Xlib-interface for the graphics, which is done in C by Urs Rohrer. Versions for Windows NT4/2K/XP, x86-Linux and Mac OS X - X11 are available. MENT offers a very useful method to do a projected emittance computation on a charged particle beam transport line. Usually one can only get a few (between 3 and 6) different views (profiles), which is by far not sufficient for conventional beam tomography programs to reconstruct the originating source. With MENT the lack of data is compensated by selecting from the infinite amount of possible solutions the one with the lowest information content consistent with the available data (maximum entropy beam tomography). At PSI the maximum entropy method used in this beam tomography code has been applied successfully at several proton beam lines (780 keV DC beam line, 72 MeV injection beam lines 1 and 2, 590 MeV beam lines near the Splitter, between Target M and E and at the peeled off beam to the Pirex target). For some more details about the application of Beam Tomography with Maximum Entropy see also reference [3].
Beam Tomography A disturbing problem for the beam tomography at the PSI proton beam lines is often the excessive, uncorrelated noise added to the measured profiles. This noise is mostly due to intensity fluctuations and position jitter of the proton beam (f = 50 Hz). By using an automatic Fast Fourier Transform (FFT) filter applied to the measured beam profiles, the quality of the reconstruction with beam tomography may be substantially improved. Fig. 1 (20 kB) shows such a noisy beam profile and the cleaning effect by applying the FFT filter with a cut-off frequency of about 16 Hz. A short résumé about the usefulness of Beam Tomography with the MENT-code (together with Transport and Turtle) has been published in the PSI Scientific and Technical Report 2000 Volume VI (Large Research Facilities) on pages 24 & 25.

Beam Tomography It should be mentioned here that the application of the beam tomography code MENT is not restricted to a proton beam. For example this Beam Tomography code may also be applied to a alpha particle beam for testing large aperture multipole magnets or to a pulsed electron beam from a linac (eg. SLS). The way this beam tomography code is adjusted today, the only restriction is the span of the measured beam profile data to not be less than about one mm. The beam profiles may be measured with different devices such as wire scanners, harps, strip detectors or photographic (CCD) cameras. Instead of gathering profile information at different locations along the beam line it may also be preferable to measure only at one location and getting the multitude of information for doing beam tomography through the variation of the optics (by controlled modification of the settings of some quadrupoles) between the source and the location of the beam profile observation device. Only non-dispersive beams are treated correctly by this version of beam tomography code (2 x 2 transfer matrices from source to the observation device[s] ).
The code is also capable of reconstructing 2D-x/y-sources from different angle projections at one location (at least 3) if the rotation matrices {Rij} for each projection are properly given in the input (see reference [4] equation 3 and the APPENDIX). The quality of such a source reconstruction with 3 views of a (hollow) cylinder may be seen by running the Test_numbers 1 and 3.

[1] Gerald Minerbo, MENT: A Maximum Entropy Algorithm for Reconstructing a Source from Projection Data, Computer Graphics and Image Processing 10 (1979) p. 48 - 68
[2] O.R. Sander, G. N. Minerbo, R.A. Jameson and D.D. Chamberlin, Beam Tomography in two and four dimensions, 1979 Linear Accelerator Conference, Montauk, NY, Sept. 9-14, 1979 Los Alamos Scientific Laboratory internal report LA-UR-79-2540
[3] Urs Rohrer and Werner Joho, Introduction of 2-Dimensional Beam Tomography for Monitoring Transverse Beam Emittances at SIN. Annual Report 1982, NL 5-6 (30 kB).
[4] C.T. Mottershead (LANL, AT-6) Maximum Entropy Beam Diagnostic Tomography. IEEE Transactions on Nuclear Science, Vol. NS-32, No. 5, October 1985

License agreement:
This version of MENT maintained by Urs Rohrer at PSI is freely available and distributable with one restriction: If you use it for some work whose results are made public in a report or a journal publication, then in a gentlemen's agreement you have to reference it properly.

PSI and the author of this program do not
guarantee the accuracy and/or usefulness
of the results achieved with this program.
The output of it is strongly dependent on
the given input and therefore the confirmation
of the correctness of all the results is the
responsibility of the user.

Get Maximum Entropy Tomography code (MENT) for x86-LINUX (tested with most modern x86-Linux versions running with kernels 2.4.x or 2.6.x), for Windows NT4/2K/XP (with MS-Interix installed) or Mac OS X - X11 via Anonymous FTP Services (before downloading, please read 00-index.txt and 1-readme.txt)

Get Maximum Entropy Tomography source code (MENT-srce) for x86-LINUX (tested with most modern x86-Linux versions running with kernels 2.4.x or 2.6.x) (before downloading, please read 00-index.txt and 1-readme.txt). Be aware that this source code is mostly legacy Fortran code ported over several platforms, OSes and compilers for the last 25 years. Currently it compiles with compat-g77/gcc-3.4.6 (Fortran-77/C/C++).

Beam Tomography Beam Tomography A bootable live CD has been created which contains among many other preinstalled programs 'MENT for Cygwin'. (Cygwin is a UNIX/Linux-like OS running on top of Windows.) It may be downloaded as iso-file ( U_R_live_CD.iso, 655 MB, instructions at 1-readme.txt). With low-speed internet connections you may download the split images.

Beam Tomography Beam Tomography Last updated by Urs Rohrer on 11-July-2007