adam meeting geneve, 09-02-2010 scdtl study for erha c. ronsivalle, l. picardi

ADAM meeting Geneve, 09-02-2010

SCDTL study for ERHA

C. Ronsivalle, L. Picardi


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€)


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


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


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)


SCDTL35 LAYOUT

Modules 3-4Modules 1-2


SCDTL35 ELECTRICAL PARAMETERS

* Include flat stems and 20% of coupling losses

Total RF power consumption= 6.57 MW


RF EFFICIENCY FLAT stems for an efficient stem cooling

Cylindric stems (diameter=5 mm): no stem cooling

P=1.4 MW


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


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


Input coordinates

Accepted coordinates in the three phase space planes

SCDTL35 output beam: transmission=46.3%


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


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


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


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


LINAC code output in these conditionsAccepted PL7 output coordinates in the three phase space planes

SCDTL35 output: beam transmission=33.7%


TSTEP code: LOSSES DISTRIBUTION IN SCDTL TANKS AND AVERAGE ENERGY OF LOST PARTICLES


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)


ERRORS AND TOLERANCES STUDY


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


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)


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


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


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


START-TO-END(7-235 MeV)


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.


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 )


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


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


NEW START TO END FROM 7 to 235 MeV

Accepted SCDTL35 output coordinates by LIGHT35

LIGHT35 output beam: transmission from the injector=30%


START TO END 7 - 235 MeV: EMITTANCE

Final un-normalizedRMS emittance:0.25 mm-mrad

Final normalizedRMS emittance:0.2 mm-mrad


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


ADDENDUM: SCDTL35 drawings

adam meeting geneve, 09-02-2010 scdtl study for erha c. ronsivalle, l. picardi

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