Paper | Title | Other Keywords | Page | ||
---|---|---|---|---|---|
IT08 | Controls and Beam Diagnostics for Therapy-Accelerators | diagnostics, controls, light-ion, synchrotron | 24 | ||
|
During the last four years GSI has developed a new
procedure for cancer treatment by means of the intensity
controlled rasterscan-method. This method includes
active variations of beam parameters during the treatment
session and the integration of 'on-line' PET monitoring.
Starting in 1997 several patients have been successfully
treated within this GSI experimental cancer treatment
program; within this program about 350 patients shall be
treated in the next 5 years. The developments and
experiences of this program accompanied by intensive
discussions with the medical community led to a proposal
for a hospital based light ion accelerator facility for the
clinic in Heidelberg. An essential part for patients
treatments is the measurement of the beam properties
within acceptance and constancy tests and especially for
the rasterscan method during the treatment sessions.
The presented description of the accelerator controls and
beam diagnostic devices mainly covers the requests for
the active scanning method, which are partly more crucial
than for the passive scattering methods.
|
|
|
||
IT09 | Diagnostics in Heavy Ion Machines | heavy-ion, diagnostics, electron, linac | 28 | ||
|
An overview of the measurements of most important beam
parameters in heavy ion machines is given. The special
characteristics of heavy ions concerning the great variety
of parameters with respect to the type of accelerator (linac,
circular machine), the species of accelerated ions as well
as their energy, beam intensity, beam emittance and time
structure are considered. The consequences for the design
of beam diagnostic systems are discussed. Typical examples
of measuring systems are given. Experimental results
taken during the long operating time of the GSI facilities,
covering a wide range of parameters, are reported.
|
|
|
||
IT11 | Beam Diagnostics, Old and New
This is essentially a repeat of 'Beam Diagnostics Revisited', invited talk given at EPAC, Stockholm, June 1998 |
diagnostics, emittance, linac, injection | 33 | ||
|
The performance of accelerators and storage rings
depends critically on the completeness and quality of their
beam diagnostic systems. It is essential to equip them
from inception with all the instruments providing the
information on the properties and the behaviour of the
beams, needed during running-in, in operation, and for
development of performance towards the design goal and
often well beyond. Most of the instruments have proven
their worth since decades, but their power has been
increased through the modern means of data acquisition
and treatment. A few new instruments have made their
appearance in recent years, some still under development
and scrutiny for their operational value and precision. The
multi-accelerator chains of todays and tomorrows big
colliders have tight tolerances on beam loss and emittance
blow-up. For beam diagnostics this means a great
challenge for precision and consistency of measurements
all along the chain.
|
|
|
||
CT01 | Measurements with a versatile Test Bench for Commissioning of the new GSI High Current Linac | emittance, rfq, pick-up, diagnostics | 45 | ||
|
For the commissioning of the new GSI prestripper a conventional
slitdetector system and a single shot pepperpot system has been
installed on a mobile test bench to measure intensity distributions in
the two transverse phase spaces. To determine intensity distributions
in the longitudinal phase space, including beam energy capacitive
pickups and newly developed diamond counters have been installed on the
test bench. The setup of the test bench provides also redundant
information for beam current, beam profile and beam position. The most
important features of all measuring systems including signal processing
and data evaluation are reported. First results from the commissioning
of the upgraded prestripper of the UNILAC at GSI are reported.
|
|
|
||
CT02 | Determination of Radial Ion Beam Profile from the Energy Spectrum of Residual Gas Ions Accelerated in the Beam Potential | space-charge, electron, emittance, acceleration | 50 | ||
|
Residual gas ions (RGI) created from collisions of
positive beam ions (BI) with residual gas atoms are
accelerated out of the ion beam by its space charge
potential. It is demonstrated that with one-dimensional
radial symmetry the radial distributions of BI density and
space charge potential can be determined from the energy
distribution of RGI radially leaving the beam tube. RGI
energy spectra were taken with an electrostatic analyser of
Hughes-Rojansky type on a 10 keV 1.5 mA He+ beam.
For comparison the radial BI density distribution was
determined with a radial wire probe, an electron beam
probe and a beam transport calculation based on an
emittance measurement located downstream.
|
|
|
||
CT12 | Preliminary Test of a Luminescence Profile Monitor in the CERN SPS | proton, vacuum, photon, injection | 95 | ||
|
In order to satisfy the tight emittance requirements of
LHC, a non-intercepting beam profile monitor is needed
in the SPS to follow the beam emittance evolution during
the acceleration cycle from 26 to 450 GeV. Beyond 300
GeV, the synchrotron light monitor can be used. To cover
the energy range from injection at 26 GeV to 300 GeV, a
monitor based on the luminescence of gas injected in the
vacuum chamber has been tested and has given
interesting results. This monitor could also be used in
LHC, where the same problem arises. Design and results
are presented for the SPS monitor.
|
|
|
||
PS05 | Recent Improvements of a Cryogenic Current Comparator for nA Ion Beams with High Intensity Dynamics | pick-up, heavy-ion, instrumentation, linac | 109 | ||
|
Former measurements of extracted ion beams from the
GSI heavy ion synchrotron SIS showed large current fluctuations
in the microsecond region with a high peak-to-average
ratio. To adapt our Cryogenic Current Comparator
(CCC) to this time structure the detectors electronics have
been carefully modified.
The most important improvement of the new DC
SQUID system affects the enlargement of the bandwidth
and the slew rate of the measuring system. In addition the
existing data acquisition system for e.g. SEMs (Secondary
Emission Monitors) was extended to digitize the CCC signals
simultaneously. Measurements of Argon beams will
be shown to demonstrate the improved capabilities of the
upgraded Cryogenic Current Comparator.
|
|
|
||
PS09 | Beam Steering With Image Processing In The Cryring Injection Beamline | quadrupole, injection, focusing, synchrotron | 118 | ||
|
By varying six quadrupoles and observing how the
beam spot moves on three fluorescent screens the beam is
aligned in the injection beamline. The method is now
automated and upgraded by using image processing of the
picture to get the position of the beam.
|
|
|
||
PS10 | Ionisation losses and wire scanner heating: evaluation, possible solutions, application to the LHC. | electron, proton, lepton, vacuum | 120 | ||
|
Harmful heating mechanisms, resulting in wire breakage,
limit the utilisation of wire scanner monitors to below
a given beam intensity. This threshold depends on the
accelerator design parameters. In lepton colliders, the
short beam bunches generate strong wake-fields inside the
vacuum pipe which are sensed by the wire and are the
predominant current limit. These effects can be minimised
by a smooth design of the monitor cross section and by
choosing a wire made of an insulating material.
A second source of energy deposition inside the wire,
also present in hadron machines, and even when the wire
material is insulating, results from collision and ionisation
of the wire material atoms by the incident beam particles.
Calculations are presented to evaluate the efficiency of
this process and a possible solution is suggested which
may reduce this limitation. An example is given for the
case of the LHC.
|
|
|
||
PS11 | Ionisation profile monitor tests in the SPS | electron, proton, space-charge, insertion | 123 | ||
|
A beam profile monitor, from DESY, based on the ionisation
of the rest gas, was installed in the SPS in 1997. Horizontal
beam profiles obtained from the extracted positive ions are
presented. It is known that in this case some broadening affects
the signal, which limits the monitor resolution. This broadening
results from the transverse momentum that the ions gain
within the space charge field of the circulating beam.
In order to improve the resolution for LHC applications, the
monitor was modified during the 1998/99 winter stop. A magnetic
focusing was incorporated. The aim is to analyse the signal
provided by collecting the electrons, rather than the ions,
of the ionised rest gas. The details of this new set-up and the
expectations for the resolution limit will be compared to the
measurement results.
|
|
|
||
PS12 | Performance of the new SPS beam position orbit system (MOPOS) | pick-up, heavy-ion, proton, extraction | 126 | ||
|
The orbit and trajectory measurement system COPOS
of the CERN SPS accelerator has been in operation since
the construction of the machine in 1976. Over the years
the system has been slightly modified in order to follow
the evolving demands of the machine, in particular for its
operation as a p-pbar collider and, since 1991, for the
acceleration of heavy ions.
In 1995 the performance of the system was reviewed
and the following shortcomings were identified:
|
|
|
||
PS14 | Comparative test results of various beam loss monitors in preparation for LHC | proton, beam-losses, simulation, electron | 132 | ||
|
Beam loss detectors will play an important role in the
protection of the superconducting LHC magnets.
Different types of detectors have been tested in the SPS
ring and secondary beam lines with a view to their
possible use for this application.
This paper describes the measurements made with:
microcalorimeters at cryogenic temperatures, PIN diodes,
ionisation chambers, scintillators, and ACEMs.
Measurements made using proton beams showing their
relative sensitivities, linearities in counting or analog
mode and minimum detection level will be presented.
|
|
|
||
PS15 | Beam profile measurements at 40 MHz in the PS to SPS transfer channel | injection, proton, radiation, kicker | 135 | ||
|
Bunch to bunch beam profile measurements provide a
valuable tool to control the injection lines to the SPS.
A fast profile monitor based on a 2.5μm Mylar coated
with Aluminium Optical Transition Radiation (OTR)
radiator, has been developed, installed and tested in the
transfer line between the PS and SPS.
The OTR beam image is focused onto a fast Linear
Multianode Photo Multiplier Tube and the associated
electronics sample and store profiles every 25ns.
The paper describes the detector design, the electronic
processing, and presents the results of different
measurements made with bunches of 109-1011 protons at 26
GeV, and bunches of 106 Pb82+ ions at 5.11 GeV/u.
|
|
|
||
PS20 | A current digitizer for ionisation chambers/SEMS with high resolution and fast resoponse | power-supply, electron, pick-up, monitoring | 147 | ||
|
A current-to-frequency converter (CFC), recently
developed, exhibits a response time up to the ms region.
The frequency limit is raised beyond 1 MHz, extending
the linear range by a factor of 100. The conversion
factor reaches 10-13 C/pulse. The converter is
employed, combined with ionization chambers (IC) and
secondary electron emission monitors (SEM), to
measure the intensity of the extracted beam in the
transfer lines adjoining GSI's heavy ion synchrotron
(SIS). Fast intensity fluctuations during the particle
spill can be observed.
Reduced hum and noise pickup, better handling and
mounting flexibility as well as reduced costs are
achieved building up the spill monitoring system with
distributed components.
|
|
|
||
PT07 | Emittance measurements at the new UNILAC-pre-stripper using a pepper-pot with a PC-controlled CCD-camera | emittance, laser, linac, ion-source | 171 | ||
|
The complex mathematical algorithms and procedures
to extract emittance data from intensity distributions
measured with a single shot pepper-pot device are
described. First results of mathematical evaluation from
the commissioning of the new GSI pre-stripper linac
structures are presented.
|
|
|
||
PT12 | Aspects of bunch shape measurements for low, intense ions beams | target, scattering, rfq, electron | 186 | ||
|
For the characterisation of the ion beam delivered by
the new High Current LINAC at GSI, the time structure
of bunches and the knowledge concerning their intensity
distribution in longitudinal phase space is of great
importance. At least 100ps time resolution and the
capability of measuring long tails in the distribution were
design parameters. Taking advantage of Rutherford-scattering
to reduce the count rate, a direct time of flight
measurement technique using diamond detectors can be
applied. First results are reported. Plans for determine the
energy of individual ions by detecting secondary
electrons emitted from a thin C foil using 1m drift are
discussed.
|
|
|