2. FCC Kicker Systems M.J. Barnes, T. Kramer CERN TE-ABT
02/12/ ETHZ visit

3. Outline of Presentation
CERN Accelerator Complex
Beam Transfer – Kicker Magnets
Kicker Magnets – brief description
Pulse generators typically used for kicker systems
The need for new developments
FCC extraction (dump) kicker system
FCC dilutor kicker system
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

4. CERN’s particle accelerators
The Large Hadron Collider (LHC):
Two beams of >1014 of protons each circulating around a 27 km ring at close to the speed of light, in opposite directions;
Made to collide in 4 detectors (ALICE, ATLAS, CMS, LHCb);
~90 µs per rotation;
At 7 TeV each proton has ~7500 times the mass of a stationary proton.
25 ns
Bunch: presently up to 1.16x1011 protons per bunch.
Up to 2808 bunches circulating per beam
LHC Beam:
Awake
LHC GeV to 7+7TEV;
SPS 25Gev to 450GeV
PS 1.4GeV to 25GeV
PSB to 50MeV to 1.4GeV
Note: relative circumference of the rings….
Many different detectors have to be used, each providing a different piece of information to physicists. To understand such a complex system, one needs to observe the phenomenon from different points of view, using different instruments at the same time.
LHC experiments
ATLAS A Toroidal LHC Apparatus, general-purpose detector. 46 metres long, 25 metres in diameter, and weighs about 7,000 tonnes;
CMS Compact Muon Solenoid, general-purpose detector. The complete detector is 21 metres long, 15 metres wide and 15 metres high. 4T magnetic field
LHCb LHC-beauty. A specialized b-physics experiment, that is measuring the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark)
ALICE A Large Ion Collider Experiment: optimized to study heavy-ion collisions.
TOTEM Total Cross Section, Elastic Scattering and Diffraction Dissociation. The detector aims at measurement of total cross section, elastic scattering, and diffractive processes.
LHCf LHC-forward, is intended to measure the energy and numbers of neutral pions (π0) produced by the collider. This will hopefully help explain the origin of ultra-high-energy cosmic rays.
MoEDAL Monopole and Exotics Detector At the LHC LHC
preaccelerators
Linear accelerators for protons (Linac 2) and Lead (Linac 3)
PS Proton Synchrotron
SPS Super Proton Synchrotron
Animation courtesy of Lorena Vega Cid
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

5. Beam transfer between accelerators
time
kicker field
intensity
injected
beam
‘boxcar’ stacking
“n”
Septum magnet
Kicker magnet
(installed in
circulating beam)
Focusing-quad
Injected beam
Circulating beam
Defocusing-quad
Field “free” region
Thin septum blade
Homogeneous field in septum
Kicker field: fast rise/fall, good flat-top, high precision timing
Beam injection, extraction, dump:
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

6. LHC Injection Kicker Magnets
LHC Transmission Line Kicker Magnet
Ferrite yoke
Magnet, in vacuum tank, with ceramic tube
Ceramic tube
Kicker Magnet
Screen conductor in slot
“Ground” on one end of outside of ceramic tube
Ceramic capacitor
LHC Injection Kicker Magnets
Baked out to 325°C to be compatible with ultra-high vacuum (~10-11 mbar in tank);
2.7m long magnet; ~3m long ceramic tube with 42 mm inside diameter, in 54 x 54 mm aperture of kicker.
Ceramic tube is a “carrier” for conductors – to screen the ferrite yoke from the high intensity LHC beam;
One end of each screen conductors is connected to ground, the other is capacitively coupled to ground;
High vacuum pressure can result in electrical breakdown.
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

7. Pulse Generators PFL and PFN based Generators
Very fast systems (30ns rise time) are mostly using PFL’s and thyratron switches (di/dt): in general deuterium thyratrons are used as the power switch for kicker systems.
“Slower” systems (0.2-3µs) are based on PFN and GTO, IGBT or MOSFET technology (stacked).
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

8. The need for new developments
Pulse Forming Line:
PFL has limitations: it should be matched to the load impedance, but coaxial transmission lines are commercially available only with certain impedances;
It is increasingly difficult to source coaxial transmission line for the highest voltage (~80 kV) kicker systems.
Suitable semiconductor switch topologies can help to solve the above problems.
~340mm
Thyratrons:
+ve: Three-gap thyratrons can hold-off 80 kV and switch 6 kA of current with a 30 ns rise-time (10% to 90%) [~150 kA/μs].
-ve: pre-fire (self turn-on without a trigger signal) is a concern for systems requiring very high reliability;
-ve: is only a closing switch  need for PFN/PFL for energy storage.
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

9. Inductive Adder R&D Traditional topology: Inductive adder topology:
n x low voltage layers
ON/OFF by MOSFETs or IGBTs
Magnetic coupling
Impedance Z
PCB
Courtesy Patrick Faure:
Magnetic core
Capacitor
Secondary
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

10. FCC Extraction Kicker System
MKD QF QD
MSD
MKBH
MKBV
TCDS
Dump Block
TCDQ
Part of a safety critical system: Up to 8.5 GJ to be safely extracted and dumped.
Extraction Kickers & Generators (MKD)
Horizontal Dilution Kickers & Generators (MKBH)
Vertical Dilution Kickers & Generators (MKBV
Septum
Initially challenging requirements. BT-Optics team developed very beneficial layout!
Started with ultra high current considerations (tr=10µs).
Evolved to a fast but segmented system for machine protection and feasibility reasons.
Unit
Extraction
Dilution
Kinetic Energy
TeV
3.3 to 50
Available length m
130
150
Deflection angle
mrad
0.13
0.21
Field rise time (0.5-90%) µs 1
Field flattop duration
≥ 333
~350
Magnet current kA
0.5 to 8 11
Output voltage range kV
~10
~20
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

11. Extraction Kicker Magnet
Preliminary Design Concept :
Based on (robust) LHC MKD design.
Outside vacuum (ceramic chamber).
Segmented system (300 units per beam):
Allows low inductance and hence fast rise time
Impact of one unit on beam <1σ
10 “hot spares” included (increases system availability)
With the help of the developed beam optics we succeed to achieve reasonable design values!
Parameters (per module)
B.dl [T.m]
0.076
k [µrad]
0.517
B [T]
0.25
Length [mm]
300
Inductance [µH]
0.38
Current [kA]
To 8
Voltage [kV]
10 *
Aperture (h/v) [mm]
36/36
* assuming additional circuit inductance (1µH)
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

12. Extraction Kicker Generator
One generator per Magnet (10 kV / 8 kA)
System rise time of 1 µs.
Challenge: Compensation stage to be designed for 330 µs:
Long flat top needs some thought (compensation circuits).
Possibly using GTO switch technology.
long “on” state duration (330 µs) – segmented system (lower current helps a lot versus very high current concept)
Promising developments within the “wide band gap” sector.
Direct laser triggering being investigated.
Again reasonable basic design values achieved but:
Reliability will be extremely important!
Possible radiation effects will be a serious issue which needs to be addressed.
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

13. Dilution Kicker System
Dump pattern crucial for survival of dump block!
Dense collaboration with FLUKA studies on dump devices.
No crossing, 1.8 mm minimum bunch separation.
Spiral seems to be the only good solution.
Painting inwards to ease hardware design.
Resulting dump radius in the region of 600 mm!
Same radiation concerns as for MKD!
Horizontal and vertical system could use the same generator design.
Vertical generators would be triggered at 90 degree of horizontal sine wave (= 50kHz).
No issue during normal operation but for asynchronous beam dumps only the horizontal dilution is available immediately. First 5 µs of beam would be painted on a horizontal line before the spiral starts. Impact to be checked.
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

14. Dilution Kicker Magnets
A very challenging system!
Highest B.dl to deliver and aperture of the vertical system increases with length.
Introduced 2 vertical magnet types.
Quadrupole after MKBH for “over focusing” in horizontal plane under study.
Short magnets to allow for 3-turn coil and higher dilution frequency.
Higher number of magnets: Impact of missing (or misbehaving) unit lower (to be optimized).
Unit
Value
B.dl Tm 35
Lever arm m
2800
Angle
mrad
0.21
Max. deflection
0.588
Design frequency
kHz 50
MKBH
Unit
MKBV1
MKBV2
max. B-field T
0.85
0.5
0.4
magnetic length m
0.9
horizontal aperture mm 62 81
104
vertical aperture 40 58
Total length ~150m
MKBH
MKBV2
MKBV1 39 48
43 m
54 m
M.J. Barnes & T. Kramer
02/12/ ETHZ visit

15. Dilution Kicker Generators
Magnet Inductance [µH]*
I [kA]*
U [kV] **
MKBH 5 9 22
MKBV1
4.8
10.8
20.5
MKBV2
4.4 11 19
* For magnet with three turn coil.
** 1µH considered for additional circuit Inductance.
Reasonable main capacitance: 1.8 µF
Amplitude decay needs to be improved to avoid getting higher density towards the centre.
M.J. Barnes & T. Kramer
02/12/ ETHZ visit