SCDTL study for ERHA
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Transcript of SCDTL study for ERHA
ADAM meeting Geneve, 09-02-2010
SCDTL study for ERHA
C. Ronsivalle, L. Picardi
ADAM meeting Geneve, 09-02-2010
TOP-IMPLART (ENEA-ISS-IFO Project in Rome) and EHRA Project (Ruvo di Puglia) do not require radioisotopes production at low energy and foresee for their protontherapy complex a completely linear structure.
In the following the design of a SCDTL structure up to 35 MeV is presented to be used for TOP-IMPLART and EHRA Projects; the first part up to 17.5 MeV is equal to the structure under development in the framework of the ISPAN Project launched by ENEA-ISS-NRT-CECOM (funded for about 500 K€)
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ISPAN (“Irraggiamento Sperimentale con Protoni per modelli cellulari ed Animali”) Project
The Project foresees the realization of a test facility at ENEA-Frascati laboratories by using as injector a PL7 425 MHz linear accelerator
SCDTL
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Outline
DESIGN CRITERIA OF SCDTL35 SCDTL35 LAYOUT AND PARAMETERS FROM DESIGN
CODE OPTIMIZATION BEAM DYNAMICS IN SCDTL35:
- LINAC code results - Matching with the 7 MeV injector (PL7) - Losses distribution (checked also with TSTEP code) - Errors and tolerances study in SCDTL35 - Start-to-end up to 235 MeV including LIGHT35 (from DeGiovanni data-
December 2009 version)
CONCLUSIONS
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Main design criteria and constraints INJECTION ENERGY: 7 MeV OUTPUT ENERGY: 35 MeV ONE 10 MW KLYSTRON WITH A POWER CONTINGENCY
OF 3 MW (P<7 MW) NUMBER OF MODULES: 4 EXTERNAL PMQs WITH A MAXIMUM GRADIENT OF 220 T/m
(useful radius for protons =2.9 mm) FROM ASTER MAIN DIFFERENCES RESPECT TO SCDTL DESIGN FOR
TOP linac (ENEA Technical Report RT/INN/9717,1997) RELEVANT FOR BEAM DYNAMICS:
-The old design assumed internal PMQ (Leff=30 mm) with an intertank distance varying in the range 7-35 MeV between 43 and 65 mm too short for allocating external PMQs (Transverse acceptance1/max, and max Lperiod)
- Higher electric field gradient (limited to12 MV/m in the old design) are required to reduce the total length: attention to keep /maxconst. In the allowed range of PMQ gradients and to avoid parametric resonances and longitudinal instability) (phase longitudinal advance l EOT)
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SCDTL35 LAYOUT
Modules 3-4Modules 1-2
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SCDTL35 ELECTRICAL PARAMETERS
* Include flat stems and 20% of coupling losses
Total RF power consumption= 6.57 MW
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RF EFFICIENCY FLAT stems for an efficient stem cooling
Cylindric stems (diameter=5 mm): no stem cooling
P=1.4 MW
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THEORETICAL BEAM DYNAMICS PROPERTIES (from DESIGN data, assuming constant normalized transverse, that means negligible coupling between transverse and longitudinal planes and perfet matched FODO lattice)
Transverse acceptance (At=r2/TWISSmax)= 8.7 mm-mrad Longitudinal
phase stable
area (foreseen phase
acceptance58.5°=3|s|)
INJECTOR: PL7 OUTPUT BEAM PARAMETERS
Exun Exun Eyun Eyun * DW * El
(100%) (rms) (100%) (rms) (deg) (keV) ( deg-MeV)
------------------------------------------------------------------------------ 6.6 (100%) 1.1 7.2(100%) 1.2 59° 93.3 5.4114.4 (90%) 4.8(90%) (at 2998 MHz) (at 2998MHz)
* Half width
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BEAM DYNAMICS: LINAC CODE RESULTS FOR AN IDEAL MATCHING BETWEEN PL7 AND SCDTL35 (distance from injector=0)
0102030405060708090
100
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5z(m)
Transmission (%)
Energy(MeV)
M1 M2 M3 M4
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Input coordinates
Accepted coordinates in the three phase space planes
SCDTL35 output beam: transmission=46.3%
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BEAM QUALITY IN THESE CONDITIONS: EMITTANCE
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5z(m)
mm
-mra
d
Exun_rms
Eyun_rms
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5z(m)
mm
-mra
d
Exn_rms
Eyn_rms
RMS unnormalized emittance at 35 MeV: 0.7 mm-mrad
RMS normalized emittance at 35 MeV: 0.2 mm-mrad
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EFFECT OF INJECTOR BUNCH LENGHTENING ON SCDTL TRANSMISSION
Bunch lenghtening due to velocity spread in a drift following the injector
transmission vs distance between injector output and center of the first PMQ on SCDTL: (matched beam on transverse planes)
0
50
100
150
200
250
300
0 20 40 60 80 100 120 140Injector-SCDTL distance (cm)
Ph
as
e h
alf
wid
th
(de
g a
t 2
99
8 M
Hz)
PL7 428 MHz
PL7 425 MHz
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MATCHING PL7 at 425 MHz – SCDTL35 (3 EMQs in a LEBT 1 m long before the PMQ at the SCDTL entrance) compatible with the current Frascati installation and ISPAN scheme
Total length (up to the middle of the PMQ at the entrance of SCDTL)=1131.74 mm
X-envelope
Y-envelope
- + - +
-----------------295--- ------------><-------150-------<--70-------150-------70---------150---------------231.74------------><15
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MATCHING PL7 AT 428 MHZ-SCDTL (3 PMQs in the a very short LEBT before the PMQ at the SCDTL entrance) to be discussed with ACCSYS
- + - +
Y-envelope
X-envelope
<--16 -><----30-----<----------------80--------------------------30-----<----------------80----------------------------30---<12.33><15
Total length (up to the middle of the PMQ at the entrance of SCDTL)=293.33 mm
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LINAC code output in these conditionsAccepted PL7 output coordinates in the three phase space planes
SCDTL35 output: beam transmission=33.7%
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TSTEP code: LOSSES DISTRIBUTION IN SCDTL TANKS AND AVERAGE ENERGY OF LOST PARTICLES
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TSTEP code: LOSSES DISTRIBUTION IN TERMS OF POWER
Plot normalization: injected current from PL7=1 A
0
0.2
0.4
0.6
0.8
1
1.2
T1 T3 T5 T7 T9T11 T13 T15 T17 T19 T21 T23 T25 T27
Lo
st
Po
we
r fo
r 1
uA
of
inje
cte
d b
ea
m (
W)
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ERRORS AND TOLERANCES STUDY
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ERRORS AND TOLERANCES: PMQsNruns=50, Random errors (uniformly distributed in |error|)
Effect on transmission:markers position on the points corresponding to a factor=0.9 on transmission for a loss with probability of 90% - Rot. angle=2°, gradient=4%, displacement=50m
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ERRORS AND TOLERANCES: TANKSNruns=50, Random errors (uniformly distributed in |error|)
Effect on transmission:markers position on the points corresponding to a factor=0.9 on transmission for a loss with probability of 90% - Field amp. error=2%, tank displacement=150 m
entire tank is displaced independently in x,y
each end of tank is independently displaced (tilt)
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ERRORS AND TOLERANCES: PHASE SHIFTSNruns=50, Random errors (uniformly distributed in |error|)
Effect on transmission:markers position on the points corresponding to a factor=0.9 on transmission for a loss with probability of 90% - error in distance between tanks=150 m, error in the length of the cells=50 m
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ERRORS AND TOLERANCES (Total Np=100K, nruns=300)PMQs: Rot. angle=2°, gradient=4%, x-y displacement=50mTANKS AND CELLS ERRORS: Field amp. error=2%, tank displacement=150 m error in distance between tanks=150m, error in the length of the cells=50 m
Prob=90% of transmission/max. transmission>50%
Prob=90% of Exn<0.28 mm-mrad,Eyn<0.29 mm-mrad
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THE LOW ENERGY SCDTL PART 7-17.5 MEV IS MORE CRITICAL RESPECT TO TOLERANCES (that can be relaxed in the last two modules)
tolerance on tank field amplitude error from 2% to 6%
tolerance on PMQ displacement from 50 m to 100 m
7-35 MeV 17.5-35 MeV
7-35 MeV 17.5-35 MeV
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START-TO-END(7-235 MeV)
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START-TO-END: SCDTL35+LIGHT35(retrieved from DeGiovanni DESIGN data-December 2009)
SCDTL35 beam portion that is transmitted up to 235 MeV in LIGHT35
The total capture drops from 33.7 % at SCDTL output to 20 % at LIGHT35 output.
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START-TO-END: possible revision of LIGHT35 to optimize the matching between the two structures and reduce losses at high energy
REASONS OF THE CAPTURE REDUCTION IN LIGHT35
parameter SCDTL35 LIGHT35 (TERA DESIGN)s -18° -13°Number of cells/tank 6 (i.e 6 ) 18 (i.e 9 ) Intertank distance at 35 MeV 3.5 4.5
With some modifications in the part at fixed energy (35-100 MeV) it is possible (as it will be shown in the next slides) to increase the longitudinal and transverse acceptance of LIGHT35, so improving the matching between the two structures and avoiding losses at high energy without getting a longer structure (inter-tank distance in the last two modules from 2.5 to 1.5 )
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LIGHT35 ORIGINALmodule phis n. tank n c ell E nerg y E nerg y g ain L eng th P eak P ower
- ° - - MeV MeV m MW1 -13 4 72 53 18 1.45 6.702 -13, -14 4 72 75 22 1.74 6.983 -14 4 72 100 25 2.01 7.004 -14 3 54 124 24 1.54 6.525 -14,-15 3 54 150 26 1.68 6.666 -15 3 54 177 27 1.80 6.547 -15 3 54 205 28 1.92 6.518 -16 3 54 235 30 2.02 6.57
T OT AL - 27 486 - 200 14.16 53.47
LIGHT35 MODIFIED (three more tanks, but no greater final length)module phis n. tank n c ell E nerg y E nerg y g ain L eng th P eak P ower
- ° - - MeV MeV m MW
1 -16 5 70 52 17 1.46 6.572 -16 5 75 74 22 1.90 6.983 -15 5 75 100 26 2.08 7.024 -15 3 54 124 24 1.54 6.575 -15 3 54 150 26 1.68 6.696 -15 3 54 177 27 1.80 6.537 -15 3 54 205 28 1.75 6.578 -15 3 54 235 30 1.84 6.71
TOTAL - 30 490 - 200 14.06 53.64
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NEW START TO END FROM 7 to 235 MeV PL7 at 428 MHz LEBT 29 cm long SCDTL35 LIGHT35 (modified)
LAYOUT:
30%
20%SCDTL35 LIGHT35
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NEW START TO END FROM 7 to 235 MeV
Accepted SCDTL35 output coordinates by LIGHT35
LIGHT35 output beam: transmission from the injector=30%
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START TO END 7 - 235 MeV: EMITTANCE
Final un-normalizedRMS emittance:0.25 mm-mrad
Final normalizedRMS emittance:0.2 mm-mrad
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CONCLUSIONS A SCDTL structure up to 35 MeV with a length <5.4 m to be used as the
first part of ERHA linac has been designed: a prototype of the first two modules up to 17.5 MeV is under realization in the framework of ISPAN Project
the transverse emittance of the PL7 output beam is inside the transverse acceptance of SCDTL. The losses are due to longitudinal mismatching due to the jump of RF frequencies
the longitudinal capture can be improved passing from 425 MHz to 428 MHz for the PL7 linac (to be discussed in the next contacts with ACCSYS)
A proper revision of the LIGHT35 structure design allows to optimize the matching between the low and high energy parts of the linac, bringing the total transmission (in absence of errors) to 30% (near to the typical values of captures in medical electron linacs) and reducing losses at high energy
The total length from the injector output from 7 to 235 MeV is 20 m
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ADDENDUM: SCDTL35 drawings
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ADDENDUM: SCDTL35 drawings