1. Introduction to Accelerator Beam Diagnostics
Dr. Peter Forck
Gesellschaft für Schwerionenforschnung (GSI) & University Frankfurt, Germany

2. Demands on Beam Diagnostics
Diagnostics is the ’organ of sense’ for the beam.
It deals with real beams in real technical installations including all imperfections.
Four types of demands leads to different installations:
Quick, non-destructive measurements leading to a single number or simple plots.
Used as a check for online information. Reliable technologies have to be used.
Example: Current measurement by transformers.
Instruments for daily check, malfunction diagnosis and wanted parameter variation.
Example: Profile measurement, in many cases ‘intercepting’ i.e destructive to the beam
Complex instruments for severe malfunctions, accelerator commissioning & development.
The instrumentation might be destructive and complex.
Example: determination of lattice functions at a synchrotron, e.g. tune
Instruments for automatic, active beam control.
Example: Closed orbit feedback using position measurement by BPMs.
Non-destructive (’non-intercepting’) methods are preferred:
The beam is not influenced
The instrument is not destroyed.

3. The Role of Beam Diagnostics
The cost of diagnostics is about 3 to 10 % of the total facility cost:
 3 % for large accelerators or accelerators with standard technologies
 10 % for versatile accelerators or novel accelerators and technologies.
Cost Examples:
The amount of man-power is about 10 to 20 %:
very different physics and technologies are applied
technologies have to be up-graded, e.g. data acquisition and analysis
accelerator improvement calls for new diagnostic concepts.

4. Relevant physical Processes for Beam Diagnostics
Electro-magnetic influence by moving charges
Physics: classical electro-dynamics
Technology: voltage & current meas., low & high frequencies
Examples: Faraday cups, beam transformers, pick-ups
Emission of photon by accelerated charges: (only for high relativistic electrons and p)
Physics: classical electro-dynamics; Technology: optical techniques (from visible to x-ray)
Example: Synchrotron radiation monitors
Interaction of particles with photons
Physics: atomic physics optics, lasers; Technology: optical techniques, particle detectors
Examples: laser scanners, short bunch length measurement, polarimeters
Coulomb interaction of charged particles with matter
Physics: atomic & solid state physics; Technology: current meas., optics, particle detectors
Examples: scintillators, viewing screens, ionization chambers, residual gas monitors
Nuclear- or elementary particle physics interactions
Physics: nuclear physics; Technology: particle detectors
Examples: beam loss monitors, polarimeters, luminosity monitors
And of cause accelerator physics for proper instrumentation layout.
Beam diagnostics deals with the full spectrum of physics and technology,
 this calls for experts on all these fields and is a challenging task!

5. Beam Quantities and their Diagnostics I
LINAC & transport lines: Single pass ↔ Synchrotron: multi pass
Electrons: always relativistic ↔ Protons/Ions: non-relativistic for Ekin < 1 GeV/u
Depending on application: Low current ↔ high current
Overview of the most commonly used systems:
Beam quantity
LINAC & transfer line
Synchrotron
Current I
General
Special
Transformer, dc & ac
Faraday Cup
Particle Detectors
Pick-up Signal (relative)
Profile xwidth
Screens, SEM-Grids
Wire Scanners, OTR Screen
MWPC, Fluorescence Light
Residual Gas Monitor
Wire Scanner,
Synchrotron Light Monitor
Position xcm
Pick-up (BPM)
Using position measurement
Transverse Emittance εtrans
Slit-grid
Quadrupole Variation
Pepper-Pot
Wire Scanner
Transverse Schottky

6. Beam Quantities and their Diagnostics II
Beam quantity
LINAC & transfer line
Synchrotron
Bunch Length Δφ
General
Special
Pick-up
Secondary electrons
Wall Current Monitor
Streak Camera
Electro-optical laser mod.
Momentum p and
Momentum Spread Δp/p
Pick-ups (Time-of-Flight)
Magnetic Spectrometer
Pick-up (e.g. tomography)
Schottky Noise Spectrum
Longitudinal Emittance εlong
Buncher variation
Pick-up & tomography
Tune and Chromaticity Q, ξ
---
Exciter + Pick-up
Transverse Schottky Spectrum
Beam Loss rloss
Particle Detectors
Polarization P
Laser Scattering (Compton scattering)
Luminocity L
Destructive and non-destructive devices depending on the beam parameter.
Different techniques for the same quantity ↔ Same technique for the different quantities.

7. Example: Diagnostics Bench for the Commissioning of an RFQ

8. Typical Installation of a Diagnostics Device
Modern trend:
High performance ADC
& digital signal processing
→ action of the beam to the detector
→ low noise pre-amplifier and first signal shaping
accelerator tunnel:
→ analog treatment, partly combining other parameters
→ digitalization, data bus systems (GPIB, VME, cPCI...)
local electronics room:
→ visualization and storage on PC
→ parameter setting of the beam and the instruments
control room:

9. The ordering of the subjects is oriented by the beam quantities:
Outline of the Lecture
The ordering of the subjects is oriented by the beam quantities:
Current measurement: Transformers, cups, particle detectors
Profile measurement: Various methods depending on the beam properties
Pick-ups for bunched beams: Principle and realization of rf pick-ups,
closed orbit and tune measurements
Measurement of longitudinal parameters: Beam energy with pick-ups,
time structure of bunches for low and high beam energies, longitudinal emittance
Beam loss detection: Secondary particle detection for optimization and protection
It will be discussed: The action of the beam to the detector, the design of the devices, generated raw data, partly analog electronics, results of the measurements.
It will not be discussed: Detailed signal-to-noise calculations, analog electronics,
digital electronics, data acquisition and analysis, online and offline software....
General: Standard methods and equipment for stable beams with moderate intensities.

10. Understanding the signal generation of various device
Goal of the Lecture
Signal generation
Valid interpretation
The goal of the lecture should be:
Understanding the signal generation of various device
Showing examples for real beam behavior
Enabling a correct interpretation of various measurements.

11. Literature on Beam Diagnostics
Conferences (with proceedings at
American: Beam Instrumentation Workshop BIW
Europe: Diagnostics and Instrumentation at Part. Acc. Conf. DIPAC
now joined as International Beam Instrumentation Conference IBIC
Books:
V. Smaluk, Particle Beam Diagnostics for Accelerators: Instruments and Methods,
VDM Verlag Dr. Müller, Saarbrücken 2009.
D. Brandt (Ed.), Beam Diagnostics for Accelerators,
Proc. CERN Accelerator School CAS, Dourdan, CERN (2009)
see
P. Strehl, Beam Instrumentation and Diagnostics, Springer-Verlag, Berlin 2006.
H. Koziol, Beam Diagnostic for Accelerators, Proc. CERN Accelerator School CAS,
University Jyväskylä, Finland, p. 565 CERN (1994),
see
J. Bosser (Ed.), Beam Instrumentation, CERN-PE-ED , Rev
P. Forck, JUAS Lecture Notes on Beam Diagnostics,
see www-bd.gsi.de/conf/juas/juas.html. 11 11

12. Appendix: Example of Beam Diagnostics Installations
The beam diagnostics installations for two example are presented:
Heavy ion LINAC, synchrotron and transport line at GSI Germany
Electron LINAC, booster and synchrotron at light source ALBA, Barcelona, Spain 12 12

13. The German Heavy Ion Accelerator Facility at GSI
German national heavy ion accelerator facility in Darmstadt
Layout:
Acceleration of all ions
LINAC: up to 15 MeV/u
Synchrotron: up to 2 GeV/u
Research area:
Nuclear physics
Atomic physics
Bio physics incl. therapy
Material research
Extension by international
FAIR facility

14. The German Heavy Ion Accelerator Facility at GSI: Overview
SIS
FRS
ESR
Ion Sources:
all elements
UNILAC
UNILAC: all ions p – U :
3 – 12 MeV/u, 50 Hz, max. 5 ms
Up to 20 mA current
Synchrotron, Bρ=18 Tm
Emax p: GeV
U: 1 GeV/u
Achieved e.g.:
Ar18+: 1·1011
U28+: 3·1010
U73+: 1·1010
ESR:
Storage Ring, Bρ=10 Tm
Atomic & Plasma Physics
Radiotherapy
Nuclear Physics

15. The German Heavy Ion Accelerator Facility at GSI: Overview
Synchrotron:
Current: 2 DCCT, 1 ACCT, 1 FCT
Profile: 1 SEM-Grid, 1 IPM, 1 Screen
Position: 16 BPM
Tune, mom. spread: 1 Exciter + BPM
1 Schottky
Ion Sources:
all elements
UNILAC
SIS
UNILAC
FRS
Transport Lines:
Current: 8 FCT
15 Part. Detec.
Profile: 10 SEM-Grid
26 MWPC
18 Screens
Position: 8 BPM
ESR
LINAC:
Current: 52 transformers, 30 F-Cups
Profile: 81 SEM-Grids, 6 BIF
Position & phase: 25 BPM
Trans. emittance: 9 Slit-Grid, 1 pepper-pot
Long. emittance: 3 devices

16. All ions, high current, 5 ms@50 Hz, 36&108 MHz
GSI Heavy Ion LINAC: Current Measurement
Faraday Cup: for low current measurement and beam stop, total 30
MEVVA
MUCIS
PIG
RFQ IH IH2
Alvarez DTL
HLI: (ECR,RFQ,IH)
Transfer to
Synchrotron
2.2 keV/u
β =
120 keV/u
β = 0.016
11.4 MeV/u
β = 0.16
Gas Stripper
U4+
U28+
All ions, high current, 5 Hz, 36&108 MHz
Foil Stripper
To SIS ↑
Transformer ACCT: for current measurement and transmission control
total 52 device
Constructed in the 70th, Upgrade 1999,
further upgrades in preparation
1.4 MeV/u ⇔β = 0.054

17. Dipole, quadrupole, rf cavity Dipole, quadrupole, transfer line
GSI Heavy Ion Synchrotron: Overview
Dipole, quadrupole,
rf cavity
acceleration
acceleration
Important parameters of SIS-18
Important parameters of SIS-18
Circumference
216 m
Inj. type
Multiturn
Energy range
11 MeV → 2 GeV
Acc. RF
0.8 → 5 MHz
Harmonic
4 (= # bunches)
Bunching factor
0.4 → 0.08
Ramp duration
0.06 → 1.5 s
Ion range (Z)
1 → 92 (p to U)
Circumference
216 m
Inj. type
Multiturn
Energy range
11 MeV → 2 GeV
Acc. RF
0.8 → 5 MHz
Harmonic
4 (= # bunches)
Bunching factor
0.4 → 0.08
Ramp duration
0.06 → 1.5 s
Ion range (Z)
1 → 92 (p to U)
injec-
tion
injec-
tion
extrac-
tion
extrac-
tion
Dipole, quadrupole,
transfer line

18. Important parameters of SIS-18
GSI Heavy Ion Synchrotron: Current Measurement
acceleration
ACCT: injected current
MHz
Important parameters of SIS-18
DCCT: circulating current
kHz
Circumference
216 m
Inj. type
Multiturn
Energy range
11 MeV → 2 GeV
Acc. RF
0.8 → 5 MHz
Harmonic
4 (= # bunches)
Bunching factor
0.4 → 0.08
Ramp duration
0.06 → 1.5 s
Ion range (Z)
1 → 92 (p to U)
FCT: bunch structure
MHz
injec-
tion
Faraday Cup: beam dump
extrac-
tion

19. The Spanish Synchrotron Light Facility ALBA
3rd generation Spanish national synchrotron light facility in Barcelona
Layout:
Beam lines: up to 30
Electron energy: 3 GeV
Top-up injection
Storage ring length: 268 m
Max. beam current: 0.4 A
Commissioning in 2011
Talk by Ubaldo Iriso: at DIPAC 2011, adweb.desy.de/mpy/DIPAC2011/html/sessi0n.htm
see also

20. The Spanish Synchrotron Light Facility ALBA: Overview
3rd generation Spanish national synchrotron light facility in Barcelona
Layout:
Beam lines: up to 30
Electron energy: 3 GeV
Top-up injection
Storage ring length: 268 m
Max. beam current: 0.4 A
Commissioning in 2011
LINAC 100 MeV
Booster 100 MeV  3 GeV
Storage Ring: 3 GeV
From U. Iriso, ALBA

21. The Spanish Synchrotron Light Facility ALBA: Current Meas.
FCT
DCCT
FCUP AE
BCM
LTB
1 FCT
1 FCUP
3 BCM
BOOSTER
1 DCCT
1 AE
BTS
2 FCT SR
Beam current:
Amount of electrons
accelerated,
transported and stored
Several in transport lines
One per ring
Abbreviation:
FCT: Fast Current Transformer
DCCT: dc transformer
FCUP: Faraday Cup
AE: Annular Electrode
BCM: Bunch Charge Monitor
Remark:
AE: Annular Electrode
i.e. circular electrode acting
like a high frequency pick-up
From U. Iriso, ALBA