1. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
BASIC CONSIDERATIONS
Present performance: 1E13p from 50 MeV to 1.4 GeV in 490 ms (1.2s cycle)
New Goal: E13p from 160 MeV to 2 GeV in 325 ms (0.6s cycle). 0.9s and 0.6s cycle data obtained from Alan and José (actual MD values)
36% more energy increase in 66% of the initial time, means roughly an average* rf power multiplied by two (1.36/0.66) together with a 3% frequency increase.
*Average means average during the acceleration itself; an increase of a super-cycle duty cycle needs to be taken into account for the power cooling system
A. Blas
PSB RF 2GeV /03/2010

2. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
Implications for the PSB low-level rf:
1.4 GeV : FREV = 1.75 MHz, FS = 446 Hz (h1,8kV)
2 GeV : FREV = 1.81 MHz, FS = 256 Hz (h1,8kV)
The increase of FREV has no impact on the beam control
The increase of B (8671 -> Gauss) requires having a B train counter well dimensioned (>17 bits).
The 0.6 s cycle is very likely to require a zero flat-top duration and thus a zero duration synchro (no theoretical problem but may be processing power limitations!?)
The change of FS (1680 Hz at 160 MeV, 256 Hz at 2 GeV (h1/8kV)) might require loop parameters to be programmed as functions (not constant)… may be this already the case !? (to be checked with Maria-Elena)
Short cycles might reduce the time reserved to download the rf parameters into the beam control system and calculate the GFA functions (to be checked with Maria-Elena and Andy)
A. Blas
PSB RF 2GeV /03/2010

3. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
Implications for the PSB transverse feedback:
Beam current multiplied by 2.07 => required power multiplied by 4.3
The increased beam rigidity (+ 30% from 1.4 to 2 GeV) doesn’t play a role except for blow-up purposes… nevertheless a multiplication by 8 of the power is foreseen!
A. Blas
PSB RF 2GeV /03/2010

4. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
Compromise at low energy:
High intensity
high space charge
must increase emittance (painting)
must keep high acceptance => φS small (for same rf voltage)
must prolong acceleration => good for dipole power supplies + good for rf power.
To have a faster cycle => increase rf voltage… and the rf power by the same amount
A. Blas
PSB RF 2GeV /03/2010

5. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
Summary:
RF power is a function of the acceleration time: the longer the acceleration the lower the power
RF power is a function of the beam current: the higher the current, the higher the required power.
RF voltage is a function of the acceleration duration: the faster the acceleration, the higher the voltage for the same acceptance.
We can either specify tough constraints for the rf power taking into account the most ambitious beam, or set lower constraints and foresee cycles lengths as a function of the intensity.
A. Blas
PSB RF 2GeV /03/2010

6. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
What can be supplied to the task force:
rf power specifications for the possible most demanding beam (2E13p, 2 GeV, 0.6 s)
Lessen rf power specifications with cycle lengths as a function of the intensity (1.2 s for 2E13p, 2 GeV),(0.6 s for <1E13p, 2 GeV)…
More specifically from Mauro: how could this be made
Information needed:
Max Bdot of the new power supply (likely to be > 35.7 G/ms = 27.5 (present max) * 11273/8671
A. Blas
PSB RF 2GeV /03/2010

7. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
New Requirements:
2E13 p per ring (maximum intensity injected from Linac 4) instead of 1E13p as presently.
2GeV maximum kinetic energy at extraction (1 and 1.4 GeV also available)
Cycle durations: 1.2 , 0.9 and 0.6 s
1.2s => inj=C275, flat-top=C765, ej=C805 => acceleration=490ms, flat-top=40ms
0.9s => inj=C175, flat-top=C575, ej=C615 => acceleration=400ms, flat-top=40ms (info A. Findlay)
0.6s => inj=C46, flat-top=C389=ej => acceleration=343ms, flat-top=0ms (info J.L. Sanchez)
A. Blas
PSB RF 2GeV /03/2010

8. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
1.4 GeV parameters
w LINAC 2
1.2 s cycle
0.9 s cycle
0.6 s cycle
C inj
275
175
C start flat-top
765
575
600
C extraction
805
615
Acc. duration
490
400
325
Flat-top duration 40
Max Bdot
22 G/ms between C555 and C635
27.5 G/ms
between C360 and C465
A. Blas
PSB RF 2GeV /03/2010

9. PSB rf Foreseen limitations with 2 E13 p at 2 GeV
PS TFB
PSB rf Foreseen limitations with 2 E13 p at 2 GeV
160 MeV
1 GeV
1.4 GeV
2 GeV
B [Gauss]
2311
6867
8671
11273
Frev [MHz]
0.992
1.67
1.75
1.81 γ
1.17
2.06
2.49
3.13
FS [Hz]
h=1 / 8kV
1680
645
446
256
Beam current
H1 value
for 2E13p
Dipolar field; Present power supply limitations:
1.2 T/s -> 2.7 T/s (max value) => 65 ms
2.7 T/s -> 0 T/s => 135 ms
A. Blas
PSB RF 2GeV /03/2010

10. Beam loading in cavities
PS TFB
Beam loading in cavities
A. Blas
PSB RF 2GeV /03/2010