# Presentation: 374476

## Beam Diagnostics Challenges in the FAIR project at GSI

**The ****FAIR**** project - **
**a **_**F**_**acility for **_**A**_**ntiproton and **_**I**_**on **_**R**_**esearch**

**Planning of ****FAIR**** beam diagnostics done by **
**Peter Forck and Andreas Peters together**
**with the GSI BD group and collaborators **

## 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 R&D 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

## FAIR – Basic Layout and Parameters (1)

- Beams now:
- Z = 1 – 92
- (protons to uranium)
- up to 2 GeV/nucleon
- Some beam cooling

## FAIR – Basic Layout and Parameters (2)

- 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

## FAIR – Basic Layout and Parameters (3)

- FAIR – Basic Layout and Parameters (3)

- Injector chain

- p-Linac (new):
- 70 mA, 70 MeV

## FAIR – Basic Layout and Parameters (4)

- FAIR – Basic Layout and Parameters (4)

## Scheme of FAIR Parallel Operation

## Research Areas at FAIR

- High EM Field (HI)               ---
- Fundamental Studies (HI & p)
- Applications (HI)

- Nuclear Matter Physics with
- 35-45 GeV/u HI beams

## 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 R&D 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 R&D phase.

## Challenges in the Accelerator Parameters (2)

- Straight section of the synchrotron tunnel with a shielded small recess building

- 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)

## 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 R&D 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 3*emittance (KV-Distribution) in the synchrotrons and 2*emittance 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.

## 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: 5×10-12 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.

## General Challenges for Beam Diagnostics (3)

- 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.

## Beam Diagnostic Challenges in Detail

- Examples of beam diagnostic challenges concerning the ring accelerators in detail and R&D 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

## Current Measurement in SIS100 (a)

| Injection (4*stacking) |  | Protons | U28+ |  |
| --- | --- | --- | --- | --- |
| Nmax |  | 4*1013 | 5*1011 |  |
| E [MeV/u] / trev [μs] |  | 2000 / 3.81 | 92 / 8.72 |  |
| Icoasting/Ibunch [A] |  | 1.6 / 8 | 0.28 / 1.45 |  |
| 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) |  |  |  |  |
| Icoasting/Ibunch [A] |  | 1.8 / 384 | 1.2 / 57 |  |

- Theoretical upper limits of currents in SIS100

## 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 ?

## 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

## 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)

## Current Measurement in SIS100 (e)

- Data sheet characteristics:
- Saturation field: 10 mT
- Specified linear range:± 0 – 7 mT
- Operating frequency: dc  1 MHz

- Example for the DC characteristics of a GMR sensor (NVE AA005)

*Measurements concerning high frequency behaviour are under way **!*

## 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

*Due to the two half shells an installation without vacuum break is possible!*

*Existing SIS18 DCCT with added new core*

*Details*

## BPM development - detector (a)

- _Curved section__ of SIS100_

- _Straight section__ of SIS100_

## BPM development – detector (b)

- 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
- Δx(f) = K(f) * Δ/Σ+ offset(f)
-  Careful mechanical design
- (high f by bunch-compression)
***R&D:*** Matching RF- and cyrogenic  requirements

- _Starting point: ESR BPM_

- _Necessity of guard rings__ (1)_

## 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!

## BPM development – detector (d)

- Present layout of SIS100 BPM version
- (elliptical shape)

- BPM parameters:
- Capacity:  ~ 100 pF
- Length:  30 cm

- For maximal beam current i.e. Nz 4x1013 e/bunch and bunch length of 25 ns:
-  Qm=4.3 x 10-7 C
-  **U=4.3 kV**

- For minimal beam current i.e. Nz 4x108 e/bunch and bunch length of 60 ns:
-  Qm=4.4 x 10-13 C
-  **U=4.4 mV**

*** **Barrier bucket behaviour (long bunches!) not studied until now!*
*** **Further adjustment of parameters needed!*

## BPM development – analog electronics (e)

*In the case of SIS100/300 the hybrid must most likely positioned in the cryogenic area!*

- From CS

- J. Belleman

- (from CERN-PS)

## 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: *

- Main board

- 4 channel ADC input board

- Scheme of *Libera* electronics

## 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:

## BPM development – data acquisition and analysis (h)

- BPM development – data acquisition and analysis (h)

- Results of offline implementation/calculation:

*Both methods **(CERN/GSI) **are under development and implementation in FPGA code; test are foreseen in the 2nd half of 2006 !*

- Measurement in SIS18  harmonic number = 4

## RGM Development – Requirements (a)

- 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*

## 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 2**nd** half of 2006!*

## RGM development – turn-by-turn readout (c)

- 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.](http://www.sensl.com/)__[SensL](http://www.sensl.com/)__[.com](http://www.sensl.com/)_)

*Up to 10**3** silicon micro pixels per** **mm**2**, dimensions scalable** *

## The Most Challenging Part of the FAIR Project ...

- The Most Challenging Part of the FAIR Project ...

- Realisation/Stage Plan
- 2007 (start of final design)                                                              2014

- Stage 1

- Stage 2

- Stage 3

## 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!