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SCDTL study for ERHA

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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€)

ADAM meeting Geneve, 09-02-2010

SCDTL

- The Project foresees the realization of a test facility at ENEA-Frascati laboratories by using as injector a PL7 425 MHz linear accelerator

ADAM meeting Geneve, 09-02-2010

- 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

ADAM meeting Geneve, 09-02-2010

- 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)

ADAM meeting Geneve, 09-02-2010

Modules 1-2

Modules 3-4

ADAM meeting Geneve, 09-02-2010

* Include flat stems and 20% of coupling losses

Total RF power consumption= 6.57 MW

ADAM meeting Geneve, 09-02-2010

FLAT stems for an efficient stem cooling

P=1.4 MW

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

ADAM meeting Geneve, 09-02-2010

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 5.411

4.4 (90%) 4.8(90%) (at 2998 MHz) (at 2998MHz)

* Half width

ADAM meeting Geneve, 09-02-2010

M1 M2 M3 M4

ADAM meeting Geneve, 09-02-2010

- Input coordinates
- Accepted coordinates in the three phase space planes
- SCDTL35 output beam: transmission=46.3%

ADAM meeting Geneve, 09-02-2010

RMS unnormalized emittance

at 35 MeV:

0.7 mm-mrad

RMS normalized emittance

at 35 MeV:

0.2 mm-mrad

ADAM meeting Geneve, 09-02-2010

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)

PL7 425 MHz

PL7 428 MHz

ADAM meeting Geneve, 09-02-2010

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

ADAM meeting Geneve, 09-02-2010

Total length (up to the middle of the PMQ at the entrance of SCDTL)=293.33 mm

X-envelope

- + - +

<--16 -><----30-----<----------------80--------------------------30-----<----------------80----------------------------30---<12.33><15

ADAM meeting Geneve, 09-02-2010

Y-envelope

- Accepted PL7 output coordinates in the three phase space planes
- SCDTL35 output: beam transmission=33.7%

ADAM meeting Geneve, 09-02-2010

ADAM meeting Geneve, 09-02-2010

Plot normalization: injected current from PL7=1 A

ADAM meeting Geneve, 09-02-2010

ADAM meeting Geneve, 09-02-2010

Nruns=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

ADAM meeting Geneve, 09-02-2010

Nruns=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)

ADAM meeting Geneve, 09-02-2010

Nruns=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

ADAM meeting Geneve, 09-02-2010

PMQs: Rot. angle=2°, gradient=4%, x-y displacement=50m

TANKS 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

ADAM meeting Geneve, 09-02-2010

7-35 MeV

17.5-35 MeV

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

ADAM meeting Geneve, 09-02-2010

ADAM meeting Geneve, 09-02-2010

- 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.

ADAM meeting Geneve, 09-02-2010

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 )

ADAM meeting Geneve, 09-02-2010

LIGHT35 ORIGINAL

LIGHT35 MODIFIED (three more tanks, but no greater final length)

ADAM meeting Geneve, 09-02-2010

- PL7 at 428 MHz
- LEBT 29 cm long
- SCDTL35
- LIGHT35 (modified)

LAYOUT:

30%

20%

SCDTL35

LIGHT35

ADAM meeting Geneve, 09-02-2010

- Accepted SCDTL35 output coordinates by LIGHT35
- LIGHT35 output beam: transmission from the injector=30%

ADAM meeting Geneve, 09-02-2010

Final un-normalized

RMS emittance:

0.25 mm-mrad

Final normalized

RMS emittance:

0.2 mm-mrad

ADAM meeting Geneve, 09-02-2010

- 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

ADAM meeting Geneve, 09-02-2010

ADAM meeting Geneve, 09-02-2010

ADAM meeting Geneve, 09-02-2010