Transcript francis_141004

ALBA RF system
why, how and other questions
Francis Perez
RF 1/33
Contents
•
•
•
•
WHY?
HOW?
WHICH?
Other questions
RF 2/33
WHY?
• we need a RF System to:
– accelerate the electron beam to high
speeds (~c) / high energy
– restore the energy loss via synchrotron
radiation of the stored e- beam
– provide a stable energy bucket to ensure
a long lifetime
RF 3/33
WHY?
• To accelerate the electron beam to high
speeds (~c) / high energy
– 1st in the LINAC:
• 90 keV to 100 MeV
– 2nd in the BOOSTER:
• 100 MeV to 3 GeV
RF 4/33
WHY?
• To restore the energy loss via synchrotron
radiation of the stored e- beam
Trevolution
Energy
881 ns
3.0 GeV
1.3 MeV
1.3 MV
Cavity Voltage
V = E . gap
eff
Time
400 mA
1.3 MeV/turn
520 KW
RF 5/33
WHY?
• provide a large stable energy bucket to ensure
a long lifetime of the stored e- beam
E/E
High Voltage
1%
3%
T
p
Low Voltage

For ALBA SR:
3.6 MV
3% Energy Aceptance
RF 6/33
HOW?
• inside the RF cavities an
electromagnetic field is stored
– and we will make use of:
F=qE
– to create a force that will
• accelerate the electrons
• create a st able well potential
RF 7/33
HOW?
F=qE
• The electrons are moving and the e-m
field oscillating
 1
E1 ( s)  
 0
E(s,t) = E1(s).E2(t)
at the cavities
1
S
0
elsewhere
110.4 m
Gap : g
t


E 2 (t )  E0 sin   RF dt   0 
t

0

Electrons are
bunched:
~10 mm long
600 mm apart
RF 8/33
HOW?
• in the LINAC
to 100 MeV
70 MW pulsed 3.5 ms
Which provides
effective ~100 MV of
accelerating voltage
for the e- beam in
~10 meters
RF 9/33
HOW?
• in the BOOSTER
to 3 GeV
1 cavity (5 cells)
60 kW cw
to produce 1.2 MV
the e- beam will
be accelerated in
~150 ms, 3 times
per second
RF 10/33
HOW?
• in the SR
at 3 GeV
N cavities
to provide 520 kW
for the beam
to provide 3.6 MV
3% energy acceptance
RF 11/33
WHICH Cavity?
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•
•
•
•
•
NC 100 MHz
NC 180 MHz
SC 352 MHz
NC 500 MHz
NC 500 MHz
SC 500 MHz
MAXlab
BNIP
SOLEIL
ELETTRA
EU
CORNELL
RF 12/33
ELETTRA
Total Voltage
3.6
No Cells/IPC
6
Type of cavity
nc
Voltage / cell
600
kV
Rshunt
3.4
MW
Cavity power
53
kW
Beam power/cav 87
kW
IPC power
140
kW
Amplifier Power 160
kW
Total Power
kW
960
MV
RF 13/33
EU project
Total Voltage
3.6
No Cells/IPC
6
Type of cavity
nc
Voltage / cell
600
kV
Rshunt
3.0
MW
Cavity power
60
kW
Beam power/cav 87
kW
IPC power
147
kW
Amplifier Power 160
kW
Total Power
kW
960
MV
RF 14/33
SC CORNELL
Total Voltage
3.6
MV
No Cells/IPC
2
Type of cavity
sc
Voltage / cell
1800
kV
Rshunt
4500
MW
Cavity power
0
kW
Beam power/cav 260
kW
IPC power
260
kW
Amplifier Power 300
kW
Total Power
kW
600
RF 15/33
Which cavity?
(1) ELETTRA
(2) EU
(3) CORNELL
DC POWER
2.5 MW
2.6 MW
2.1 MW
WATER
COOLING
220 m3/h
230 m3/h
140 m3/h
Cavity Wall
Dissipation
Cavity Wall
Dissipation
Refrigerator
Turbines
RF 16/33
Which cavity?
SPACE
COST
ESTIMATION
(1) ELETTRA
(2) EU
(3) CORNELL
2 x 2.9 m
2 x 2.9 m
2 x 3.3 m
3 cavities in
one 4 m
straight
3 cavities in
one 4 m
straight
1 cavity in
one 4 m
straight
9.3 M€
9.9 M€
10.6 M€
6 x 1.55 M€
+600 k€
+1300 k€
6 x 1.65 M€
2 x 5.3 M€
RF 17/33
Which cavity?
COST
DIFFERENCES
(1)
ELETTRA
(2) EU
(3) CORNELL
INVESTMENT
0
+600 k€
+1300 k€
+2400 k€
+3000 k€
0
0
0
+900 k€
+2400 k€
+3600 k€
+2200 k€
+200 k€
+1400 k€
0
RUNNING (10y)
(6000 h/year, 0.1 €/kWh)
MAN POWER (10y)
(1.5 man/year)
TOTAL
COST DIFFERENCE
OVER 10 YEARS
SPACE, SERVICES and COST are NOT DECISION FACTORS
RF 18/33
Other questions
HOM
instabilities
A RF cavity has more than just the
fundamental resonance frequency at 500 MHz
HOM strengh [a.u.]
1E+ 04
HOMs
1E+ 01
1E-02
1E-05
490
540
590
640
690
740
Frequency [MHz]
RF 19/33
HOM instabilities
When a multiple of the revolution frequency „hits“ a
HOM a resonance condition arise and a instability is
created.
fHOM = n frev (plus sidebands)
Stable
Instable
229 frev
-fs
229 frev
+fs
a.u.
a.u.
Long. mode
excited
621.76
621.81
621.86
621.91
Frequency [MHz]
621.96
621.76
621.81
621.86
621.91
621.96
Frequency [MHz]
RF 20/33
Comparison: Longitudinal HOMs
Long Impedance [kOhm]
1000,00
ZII Threshold
ELETTRA/6
EU
100,00
SC/3
10,00
1,00
0,10
0,01
500
1000
1500
2000
2500
3000
Freq [MHz]
Stability threshold for 400 mA
Cavity temperature tuning should reduce
the ELETTRA HOMs impedances
RF 21/33
Comparison: Transverse HOMs
Transverse Impedance [kOhm/m]
1000,0
100,0
10,0
CORNELL
1,0
Zy Threshold
Zx Threshold
ELETTRA/6
EU
0,1
500
700
900
1100
1300
1500
1700
1900
Freq [MHz]
Stability threshold for 400 mA
Stability because the cavities are
in a low beta section (2 m)
RF 22/33
WHICH CAVITY?
Beam stability
vs.
Beam availability
SC assures beam stability, but recovery time after failure
is longer…
NC has shorter recovery time after failure, but needs
extra care to assure beam stability
RF 23/33
Cavities
NC RF
Cooling Rack
Klystron
HVPS
RF 24/33
SC RF
Dewar
Turbines
Valve Box
Gas reservoir
Cavity
RF 25/33
Other questions
Total Voltage
Number Cells
Voltage per cav
RF Amplifier
NC
3,6 MV
6
600 kV
Shunt Impedance
3,4 Mohm
Cavity power
53 kW
Beam power / cell
87 kW
IPC power
Amplifier Power
Number Amplifiers
140 kW
160 kW
6
RF 26/33
Other questions
160 kW amplifier (IOTs)
HVPS + Amplifier
160 kW
CAVITY
RF Amplifier
NC
HVPS + Amplifier
160 kW
CAVITY
… x 6
RF 27/33
Other questions
RF Amplifier
SC
Total Voltage
Number Cells
3,6 MV
2
Voltage per cav
1800 kV
Shunt Impedance
4500 Mohm
Cavity power
0,4 kW
Beam power / cell
260 kW
IPC power
260 kW
Amplifier Power
Number Amplifiers
>280 kW
2
RF 28/33
Other questions
RF Amplifier
300 kW amplifier (klystron/IOT)
HVPS +Amplifier
300 kW
CAVITY
SC
HVPS + Amplifier
300 kW
CAVITY
x 2
RF 29/33
300 kW Amplifier:
Klystron
vs IOTs combination
RF 30/33
300 kW Amplifier
IOT combination via a cavity combiner:
80
80
300 kW
HVPS
CAVITY
80
80
RF 31/33
Cavity combiner
We want to produce a power prototype
E. Wooldridge, ASTeC
E. Wooldridge, ASTeC
RF 32/33
SUMARY
• RF is needed at:
– LINAC
• turn key system
– BOOSTER
• 5 cell cavity, 60 kW
– Storage Ring
• NC vs SC under discussion
• Klystron vs IOTs
• Cavity combiner prototype
RF 33/33