Download PSB magnetic cycle 2GeV_2

PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Specifications
1.
2.5E13 p from 160 MeV to 2 GeV
2.
Current in bending magnets < 2267 ARMS +10% = 2493 ARMS with 1.2 second
cycle (no modification of the cooling circuit).
3.
Bdot max = 38 G/ms assumed value {= 28 G/ms (present)* 5358 A (2GeV) /
4027 A (1.4 GeV)}
4.
Cavity voltage and current taken as free parameters.
5.
Longitudinal space charge effects taken into account (assuming elliptic energy
distribution)
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simplifications
1.
Pure h=1 acceleration
2.
Inductive and resistive wall effect neglected (impedance value to be asked for,
but practically assumed to be low !?). The inductive effect counteracts the
space charge effect.
All these (pessimistic) simplifications lead to conservative figures
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Longitudinal space charge effect
Total coupling impedance:
Inductive and resistive wall neglected
Z0 = 377 Ω
Circular beam pipe approximation (real value to be
checked for)
Parasitic voltage superimposed (each turn) to the accelerating
voltage (space charge only):
A. Blas
2 GeV magnetic cycle
12/05/2010
3
PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Longitudinal space charge effect
Parasitic voltage superimposed (each turn) to the accelerating
voltage (space charge only):
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simulation 1: injection at 1.2 T/s, bucket filled up to 80 % with 2.5E13p (1.024 eV.s)
The acceleration lasts 330 ms with a 5 ms flat-top (490 ms presently)
I MPS = 2341 ARMS (1.2 s cycle) < 2493 ARMS;
Total magnetic cycle length from 0G to 0G = 700 ms with 38 G/ms max Bdot.
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simulation 1: Limitation of Bdot to 38 G/ms (28 G/ms = present max)
The required h1 cavity current for the acceleration = 8.73 AP (present max = 3AP)
DC current at 2 GeV= 7.2 A = 2.5E13*1.6E-19*1.8E6 MHz
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simulation 1: The bucket is full (1.024 eV.s +20%) during the first 225 ms of acceleration
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simulation 1: The cavity voltage has been increased to compensate for space charge effects
The net voltage experienced by the beam is 8 kV along the cycle
The required h1 cavity voltage is 11.3 kVP (present max = 8kVP). The beam h1 current
goes up to 14.3 AP. This value is dealt with by the tuner loop (when there one!)
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simulation 1: The beam peak-peak current goes up to 52.4 AP-P = 45.2 AP (52.4 –
7.2 DC). With a resonant cavity only, the h1 current was dealt with by the tuner
loop. With a wideband cavity this current needs to be supplied!
With a narrow-band cavity, the beam-loading instability needs to be checked for.
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Simulation 1:
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
Conclusion:
These simulations concerns h1 uniquely, for a single harmonic acceleration made as
fast as possible with a 1.2 eV.s beam emittance and a max 38 G/ms Bdot . The
requirement should be lessened (not much) in a dual harmonic context.
The h1 cavity voltage should provide more than 11.3 kVP
Its current available for acceleration should be higher than 8.73 AP (Narrow band
cavity)
It should deal with 45.2 AP of beam current (effective current with a wideband
cavity, beam loading instability to be checked with narrow-band cavity)
Slowing down the acceleration allows for a lower current demand in a narrow band
cavity only.
With the fast cycle which has been sketched, the power dissipation in the bending
magnets is just below the maximum tolerated (2341 < 2493 ARMS).
A. Blas
2 GeV magnetic cycle
12/05/2010
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PSB magnetic cycle
160 MeV to 2 GeV with 2.5E13 protons per ring
To be done:
Make simulations with h=2 and more precise model of the MPS
Check for beam loading instabilities with narrow band cavities
Check transverse space charge effects
A. Blas
2 GeV magnetic cycle
12/05/2010
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