1. "Research and Development in Beam Diagnostics"
"PS days"
Evian, January 24th - 26th 2001
Enrico Bravin
CERN
Geneva, Switzerland
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

2. Several studies are going on inside the BD group in order to fulfil the needs and requests of the CPS complex
Fast SEM grids and quadrupole pickup for injection studies
Gas scintillation profile monitors
DC current transformers for LHC (low intensity pilot beam)
AC current transformers for short bunches (nTOF beam)
Ion pencil and ion curtain profile monitors
Neutral beam profile monitors
Beam ionisation profile monitors
New beam loss monitor system
e-cooling for the LEIR machine
Replacement of the multi-wire proportional chambers
Use of digital receivers in digital beam signal analysis
New BPM electronics i.e. normaliser and head amplifier for the PS
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

3. Injection studies using fast SEM grids and quadrupole pickup
The dispersion function of the transfer line must be matched to the dispersion function of the ring. If this is not true, the injected beam will oscillate around the nominal orbit and will lead to an emittance growth.
A similar effect happens for a betatron function mismatch. In this case it is the beam size which oscillates instead of the beam position, but the result is still an emittance blow-up.
Accelerator
Transfer
line
Dispersion
Fast charge amplifier
24 wires either ver. or hor.
40MHz 8bits flash ADC in free running
2k memory per channel
Samples 30 turns
calculates profiles each turn (size and pos)
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

4. The SEM grid can record the wire signals on every turn.
Dispersion mismatch
The SEM grid can record the wire signals on every turn.
Beam size and positions can thus be calculated on a turn by turn basis.
Accelerator
Transfer
line
Beam orbit
Position
Turn
SEM grid
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

5. Fast SEM grids
The signals of the 24 wires are sampled at 40 MHz and stored into 24 buffers,
2 kB each.
The single passage signal is then reconstructed and the beam profiles calculated.
The 2 kB buffers allow the acquisition of ~30 consecutive turns.
Fast charge amplifier
40MHz
8 bits
ADC
2k buffer
2 X 24 wires
SEM grids
Insertion
mechanism
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

6. Some injection studies results
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

7. Some injection studies results
Normalised horizontal
beam size
Normalised
horizontal
dispersion
(beam position)
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

8. PS Quadrupole Pick-up Design finished and tested in the lab
Instrument comparison
Design finished and tested in the lab
Very good CMRR obtained
Two pick-ups will be installed in PS section 3 and 4 (on schedule!)
Correction for beam position
Contributed by Andreas Jansson PS-OP

9. Use of digital receivers in signal processing
Antenna RF
Amp X IF
Demod.
Audio
Speaker
Local
Oscillator
Heterodyne
Analog Receiver IF  RF
Antenna RF
Amp X
Digital
Low
Pass
Filter
DSP
Demod.
D/A
Speaker
Local
Oscillator
Digital Receiver
A/D
conv.
Sin
Cos
Signal from longitudinal pick-up's
Either coherent (bunched) or incoherent (coasting) signal
Down converted to DC and windowed
DSP controls the DRX's and interfaces to VME
Calculates the Power Density Spectrum
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

10. The Digital Receiver -based system for antiproton beam diagnostics
DRX-BASED SYSTEM OVERVIEW
It implements a fast, on-line controllable spectrum analyser that measures N, p/p, fREV from longitudinal PU signals.
Maria Elena Angoletta, PS / BD

11. The Digital Receiver -based system for antiproton beam diagnostics
DIGITAL RECEIVER BOARD
Digital Down Converter (DDC): "h/w pre-processor" for DSP!
Strongly rejects aliased signals
Reduces DSP workload
Maria Elena Angoletta, PS / BD

12. The Digital Receiver -based system for antiproton beam diagnostics
p / p (multiple injection)
Frev [Mhz]
Maria Elena Angoletta, PS / BD

13. Ion pencil profile monitor
The ions interact with the electromagnetic field of the beam and get deflected.
The magnitude of this deflection depends on the impact parameter and the charge distribution of the analysed beam (profile).
By analysing the deflection vs. impact parameter function one can obtain the beam profile.
Source
Ions
Beam
Detector
Deflection
Angle
2-5 kV
Iions=~nA
Rions=0.1 mm
profile= d/dy theta(y)
Limit on the Ion energy (min deflection)
scan time down to a few us
curtain has more difficult data treatment
shadow only qualitative info (beam image)
resolution ~ 0.1 mm
Imin 10^10 per bunch
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

14. Ion curtain profile monitor
A profile measurement can be obtained by scanning the ion beam through the particle beam.
An alternative to the scan would be creating an ion curtain instead of a pencil beam, and using a 2D detector (e.g. CCD).
The ion curtain is obtained using a narrow slit in front of a large "cylindrical" ion beam.
The deflection vs. impact parameter is then obtained from a single image.
Beam
Ion Curtain
Detected ions
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th

15. C.Dimopoulou and R. Maccaferri
Ion curtain image
C.Dimopoulou and R. Maccaferri

16. Post-acceleration and focusing
Ion pencil setup HV
417
346 50
Pumping
Ion Beam
Proton Beam
32 Channel Collector
Post-acceleration and focusing
Deflecting Plates
Vacuum Valve
Ion Gun
Argon Inlet Valve
HV Insulator
C.Dimopoulou and R. Maccaferri

17. Conclusions
I would like to thank all those who helped me preparing this talk for their valuable contributions.
I would also like to apologise to those, in BD, who did not see their work mentioned during this talk.
There was in particular no mention to developments related to CTF-3, CLIC and neutrino factories. I did not forget them, but their status is not yet sufficiently well defined.
Let me conclude by saying that by presenting the work done by other people I had the opportunity to discover many aspects of BD I was unaware of and to learn a lot about several new subjects.
Enrico Bravin CERN R&D in Beam Diagnostics PS days - Evian, January 25th