Beam Diagnostics Challenges in the FAIR project at GSI

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Beam Diagnostics Challenges in the FAIR project
at GSI
The FAIR project - a Facility for Antiproton and
Ion Research
Planning of FAIR beam diagnostics done by Peter
Forck and Andreas Peters together with the GSI BD
group and collaborators
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Outline

• The FAIR project a short introduction to the
  accelerator parameters and the facility layout
  and operation modes as well as the research aims
• Challenges in the accelerator parameters
• Linked general challenges for the beam diagnostic
  equipment (diversity and dynamics)
• Examples of beam diagnostic challenges in detail
  and RD for possible solutions
• Current measurement in SIS100 from dc to short
  single bunch operation
• BPM systems for the cryogenic synchrotrons with
  varying acceleration frequencies
• Turn-by-turn profile measurement (RGM) in
  synchrotrons and storage rings with high
  repetition rates (MHz) under UHV conditions
• Summary and outlook

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FAIR Basic Layout and Parameters (1)
Beams now Z 1 92 (protons to uranium) up to
2 GeV/nucleon Some beam cooling
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FAIR Basic Layout and Parameters (2)
Final facility layout with all planned
buildings Tunnel for SIS100/300 at a depth of
about 17m to comply with the requirements of
radiation safety
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FAIR Basic Layout and Parameters (3)
p-Linac (new) 70 mA, 70 MeV
Injector chain
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FAIR Basic Layout and Parameters (4)
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Scheme of FAIR Parallel Operation
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Research Areas at FAIR
Nuclear Matter Physics with 35-45 GeV/u HI beams
High EM Field (HI) --- Fundamental
Studies (HI p) Applications (HI)
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Challenges in the Accelerator Parameters (1)

• Fast cycling superconducting magnets For SIS
  100 superconducting magnets (2 T) with 4 T/s
  ramping rate are required. SIS 300 will be
  equipped with 6 T (1 T/s) dipole magnets. The
  optimization of the magnet field quality for low
  loss, high current operation with beams filling
  large parts of the acceptance is of great
  importance.
• Control of the dynamic vacuum pressure caused by
  beam loss induced desorption of heavy molecules,
  which can cause the rapid increase of the
  residual gas pressure ? a novel collimation
  concept is presently under test at the SIS18.
• Cooled secondary beams Fast electron and
  stochastic cooling at medium and at high energies
  will be essential for experiments with exotic
  ions and with antiprotons.
• High RF voltage gradients The fast acceleration
  and bunch compression of intense heavy-ion beams
  down to 60 nanosecond bunch length (protons 25
  ns) requires compact RF systems. Complex RF
  manipulations with minimum phase space dilution
  and the reduction of the total beam loading in
  the RF systems are important RD issues.
• Operation with high brightness, high current
  beams The synchrotrons will operate close to the
  space charge limits with tolerable beam losses of
  the order of a few percent. The control of
  collective instabilities and the reduction of the
  ring impedances is a subject for the RD phase.

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Challenges in the Accelerator Parameters (2)
Cross section of the synchrotron tunnel with an
inner size of 5 x 4 m2, SIS100 (bottom) and
SIS300 (top) cryostats are shown with cryogenic
bypass lines (yellow)
Straight section of the synchrotron tunnel with a
shielded small recess building
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General Challenges for Beam Diagnostics (1)

• Despite quite different beam parameters of the
  FAIR synchrotrons and storage rings, common
  realizations of SIS100, SIS300 and all storage
  ring diagnostics are mandatory to save man-power
  and costs during the RD phase and enable a cost
  reduction due to the large quantities during the
  construction phase.
• Large dynamic range, e.g. in SIS100 from low
  currents beams for adjustments up to space charge
  limited intensities of heavy ions, from long
  bunches at injections up to short pulses after
  bunch rotation / compression.
• Because the acceptance was limited to 3emittance
  (KV-Distribution) in the synchrotrons and
  2emittance in the transfer lines , a precise
  alignment of the beam in the vacuum pipe is
  strongly advised. The beam diagnostics system has
  to allow a precise orbit measurement and the
  capability for online feedback on the closed
  orbit, on the betatron tune, on chromaticity and
  on coupling.
• If the loss budget in the superconducting
  synchrotrons is only a few percent, current
  measurements with high accuracy (10-4) for
  controlling beam losses are mandatory.

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General Challenges for Beam Diagnostics (2)

• Due to the compactness of all accelerators the
  repetition rates are quite high (up to the MHz
  region), which is a challenging task e.g. for
  turn-by-turn profile measurements based on a RGM
  system.
• Additional constraints have to be fulfilled,
  which are sometimes challenging
• installations in cryogenic parts of the
  accelerators,
• UHV conditions (pressure 510-12 mbar) and
• high radiation levels.
• The complex, quasi-parallel operation scheme
  demands a highly reliable and flexible data
  acquisition system adapted to the fast pulsed
  machines parameters.
• Complicated scheme of transport lines with high
  diversity of magnetic rigidities.

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General Challenges for Beam Diagnostics (3)

• Schematic view of FAIR beam transport lines
• Total length of about 2350 m of allbeam lines
  (excluding Antiproton-Separator, FLAIR beam
  lines, ...), divided in 46 sections with
  differing parameters.
• In the transfer lines the high dynamic range of
  intensities and energies as well as ion species
  leads to the necessity of destructive measurement
  methods needed for low currents and in parallel
  to non-destructive devices for high currents
  which would destroy any material in the beam
  optical path.

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Beam Diagnostic Challenges in Detail

• Examples of beam diagnostic challenges concerning
  the ring accelerators in detail and RD for
  possible solutions
• Current measurement in SIS100 from dc to short
  single bunch operation (operating bandwidth of 10
  kHz)
• BPM systems for the cryogenic synchrotron
  environment with varying acceleration frequencies
• Turn-by-turn profile measurement (RGM) in
  synchrotrons and storage rings with high
  repetition rates (MHz) under UHV conditions

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Current Measurement in SIS100 (a)
Theoretical upper limits of currents in SIS100
Injection (4stacking) Injection (4stacking) Protons U28
Nmax 41013 51011
E MeV/u / trev µs 2000 / 3.81 92 / 8.72
Icoasting/Ibunch A 1.6 / 8 0.28 / 1.45
After acceleration After acceleration After acceleration After acceleration After acceleration
E GeV/u / trev µs 26 / 3.62 2.38 / 3.76
Icoasting/Ibunch A 1.8 / 8.8 0.6 / 3.2
After bunch merging compression (h 8 ? 1, bunch length 25/60 ns) After bunch merging compression (h 8 ? 1, bunch length 25/60 ns) After bunch merging compression (h 8 ? 1, bunch length 25/60 ns) After bunch merging compression (h 8 ? 1, bunch length 25/60 ns) After bunch merging compression (h 8 ? 1, bunch length 25/60 ns)
Icoasting/Ibunch A 1.8 / 384 1.2 / 57
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Current Measurement in SIS100 (b)
Solutions a) Use the NPCT of Bergoz an
installation in SIS18 is scheduled for August
2006 and tests starting in October 2006
Question Will the feedback loop of the NPCT work
stable under high current bunched beam condition
(bunch frequency of some MHz) ?

Severe problem of GSI DCCT Above specific
levels of beam current and/or revolution
frequency the loop starts to oscillate (right).
Mostly it gets back control. But Did it settle
to the correct working point ?
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Current Measurement in SIS100 (c)
Solutions b) Design of an alternative current
measurement based on the idea of a clip-on
ampere-meter with a GMR sensor in the gap of a
toroidal core (collaboration with University of
Kassel, Germany).

Simulated magnetic flux in a slit toroidal core
Scheme of an clip-on ampere-meter
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Current Measurement in SIS100 (d)
Assuming a measurement bandwidth of 10 kHz, the
resolution of different GMR sensors is in the
order of 100 nT
Resolution measurement of different GMR sensors
(by NVE corporation)
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Current Measurement in SIS100 (e)
Example for the DC characteristics of a GMR
sensor (NVE AA005)
Data sheet characteristics Saturation field 10
mT Specified linear range 0 7 mT Operating
frequency dc ? 1 MHz
Measurements concerning high frequency behaviour
are under way !
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Current Measurement in SIS100 (f)
Construction of a first test set-up with a split
core (either VITROVAC 6025 F or CMD 5005 from CMI
ferrite) and two gaps for sensor positioning to
be built in SIS18 in autumn 2006
Details
Existing SIS18 DCCT with added new core
Due to the two half shells an installation
without vacuum break is possible!
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BPM development - detector (a)
Curved section of SIS100
Straight section of SIS100
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BPM development detector (b)
Starting point ESR BPM

• Different types of BPMs are necessary
• SIS100 version elliptical, cryogenic
• SIS300 version round, cryogenic
• Storage rings large aperture up to 300 mm,
  normal temperature env., but high bakeout
  temperatures

Position sensitivity and linearity For shoe-box
type calculated ?x(f) K(f) ?/S offset(f) ?
Careful mechanical design (high f by
bunch-compression) RD Matching RF- and
cyrogenic requirements
Necessity of guard rings (1)
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BPM development detector (c)

• Necessity of guard rings (2)
• Cross talk between plates in one plane (should be
  low!)
• Simulations on ESR type

Geometry Structure on ceramics Metal plates
no guard ring 1mm gap -5.1dB -7.9dB
no guard ring 2mm gap -8.1dB -10.8dB
with guard ring -20.8dB -22.5dB
separation rings on the ground potential

• Metal plates seem to be the better choice, but
• Mechanical stability of an arrangement of
  numerous single metal plates is poor due to
  experience from collaborators in Dubna
  (Nuclotron)!
• Structure on ceramics chosen!

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BPM development detector (d)
For maximal beam current i.e. Nz 4x1013 e/bunch
and bunch length of 25 ns ? Qm4.3 x 10-7 C ?
U4.3 kV
Present layout of SIS100 BPM version (elliptical
shape)
 
For minimal beam current i.e. Nz 4x108 e/bunch
and bunch length of 60 ns ? Qm4.4 x 10-13 C ?
U4.4 mV
BPM parameters Capacity 100 pF Length 30 cm
? Barrier bucket behaviour (long bunches!) not
studied until now! ? Further adjustment of
parameters needed!
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BPM development analog electronics (e)
(from CERN-PS)
J. Belleman
 
From CS
In the case of SIS100/300 the hybrid must most
likely positioned in the cryogenic area!
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BPM data acquisition and analysis (f)
Behind the amplifier chain no additional analog
signal treating ? direct digitization! Common
EU-FP6-initiative of GSI, CERN and
Instrumentation Technologies for a digital data
evaluation platform for fast cycling hadron
machines with varying frequencies
 
Scheme of Libera electronics
Main board
4 channel ADC input board
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BPM development data acquisition and analysis
(g)

• Two different approaches for data evaluation are
  under development now
• CERN digital version of classical base line
  restoring and PLL implementation using RF
  frequency input and phase tables
• GSI Free running algorithm with the following
  implementation

 
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BPM development data acquisition and analysis
(h)
Results of offline implementation/calculation
Measurement in SIS18 ? harmonic number 4
 
Both methods (CERN/GSI) are under development and
implementation in FPGA code test are foreseen in
the 2nd half of 2006 !
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RGM Development Requirements (a)

• Parameters given by the machines
• Revolution frequency
• in SIS 100/300 110 280 kHz
• in the Storage Rings 125 kHz 1.4 MHz
• Beam pipe apertures
• in SIS 100/300 135 65 mm2, resp. 90 mm in
  diameter (SIS300)
• in the Storage Rings up to 300 mm in diameter
• adaptive spatial resolution down to 0.1 mm (rel.
  1) necessary due to cooled beams
• Transversal measurement range 100 mm

 

• Turn-by-turn readout necessary e.g. for matching
  of the injected beam emittance orientation and
  dispersion setting with respect to the acceptance
• Detection of secondary e-/ions (? conversion
  with e.g. phosphor P47) , thus
• E-field (E?50 V/mm, 1 in-homogeneity) and
• B-field for guidance (B?0.03 T, 1
  in-homogeneity) ? compact because of limited
  space
• Read-Out Modes a) high resolution measurement
  on ms time scale with CCD camera
• b) turn-by-turn array of 100 photo-diodes or
  multi-anode PM or SiPM

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RGM development mechanical design (b)

• First design of RGM with magnets, but the
  following changes are necessary
• Possibility of change between CCD and
  multi-diode readout
• Due to low magnetic rigidities in the storage
  rings compensations of the applied magnetic
  fields of the RGM are necessary ? more complex
  magnet installations
• Alternative design with permanent magnets is
  under calculation at ITEP, Moscow

 
First test of RGM version with CCD readout, but
without magnetic field are foreseen in
collaboration with FZ Jülich at their COSY proton
storage ring in the 2nd half of 2006!
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RGM development turn-by-turn readout (c)
Alternative sensor for turn-by-turn readout
Silicon Photomultiplier (B. DOLGOSHEIN et al.,
MEPI, Moscow) First commercial sensor on the
market (www.SensL.com)
Up to 103 silicon micro pixels per mm2,
dimensions scalable
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The Most Challenging Part of the FAIR Project ...
Realisation/Stage Plan 2007 (start of final
design)
2014
Stage 1
Stage 2
Stage 3
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Acknowledgement
Instead of a summary Thanks to all colleagues
and collaborators contributing to this talk with
their papers and pictures! Thanks to our small
technical review board (Tom Shea and Hermann
Schmickler) for valuable discussion and their
consulting! Thanks for your attention!