TERA Foundation

U. Amaldi, A. Degiovanni

Silvia Verdú Andrés

November 23, 2011CLIC RF structure development meeting

Expected Performances of TERA High-Gradient Accelerating Structures

Motivation

The hadrontherapy community demands a compact, reliable accelerator with the appropriate beam performances for tumour treatment with ions.

Motivation

The hadrontherapy community demands a compact, reliable accelerator with the appropriate beam performances for tumour treatment with ions.

The linac length could be reduced if high accelerating gradients (~ 35 MV/m) were achieved for an acceptable value of breakdowns (BDR ~ 10-6 bpp/m), as breakdows compromise the machine reliability.

CABOTO is a copper standing-wave Side-Coupled Linac operating at 5.7 GHz.

Motivation

The hadrontherapy community demands a compact, reliable accelerator with the appropriate beam performances for tumour treatment with ions.

The linac length could be reduced if high accelerating gradients (~ 35 MV/m) were achieved for an acceptable value of breakdowns (BDR ~ 10-6 bpp/m), as breakdows compromise the machine reliability.

Which are the expected high gradient performances for such a machine?

CABOTO is a copper standing-wave Side-Coupled Linac operating at 5.7 GHz.

Experimental evidence

- TERA 3 GHz single-cell cavity……………………………………………….… tests ongoing

- TERA 5.7 GHz single-cell cavity……………………………………….……… tuning

- Frascati@KEK 5.7 GHz structure…..........................……………… tested!

- Several structures at 12 and 30 GHz………………………………..……. scaling laws but applicability?

TERA 3 GHzFrascati@KEK 5.7 GHz

constBDRtS pulsec 515

*scaled to BDR = 10-6bpp/m; tp=200 ns

The Frascati@KEK structure is a 5.7 GHz travelling-wave (TW) structure made in copper. It has been designed to accelerate relativistic electrons (Es/E0 ~ 2).

The structure was tested with a 0.2 ms-long RF pulse.

Structure characteristics

The Frascati@KEK structure is a 5.7 GHz travelling-wave (TW) structure made in copper. It has been designed to accelerate relativistic electrons (Es/E0 ~ 2).

The structure was tested with a 0.2 ms-long RF pulse.

Structure characteristics

CABOTO is a standing-wave (SW) structure made in copper. It has been designed to accelerate non-relativistic hadrons. Therefore, accelerating cells present «noses» in order to improve acceleration but then Es/E0 ~ 4—5.

Typical RF pulse for therapy application would be 2 ms-long. « nose »

Assumptions

The Frascati@KEK structure is a 5.7 GHz travelling-wave (TW) structure made in copper. It has been designed to accelerate relativistic electrons (Es/E0 ~ 2).

The structure was tested with a 0.2 ms-long RF pulse.

Structure characteristics

CABOTO is a standing-wave (SW) structure made in copper. It has been designed to accelerate non-relativistic hadrons. Therefore, accelerating cells present «noses» in order to improve acceleration but then Es/E0 ~ 4—5.

Typical RF pulse for therapy application would be 2 ms-long.

- Applicability of results of TW to SW.- Validity of modified Poynting vector and associated scaling laws. - Validity of pulse length scaling laws.

« nose »

Scaling and expected performances

constBDRtS pulsec 515

*scaled to BDR = 10-6bpp/m; tp=200 ns

Frascati@KEK 5.7 GHz

Scaling and expected performances

constBDRtS pulsec 515

*scaled to BDR = 10-6bpp/m; tp=200 ns

Frascati@KEK 5.7 GHz

Scaling and expected performances

constBDRtS pulsec 515

*scaled to BDR = 10-6bpp/m; tp=200 ns

Frascati@KEK 5.7 GHz

Attention: Z, Sc/E0 and Rbore affect E0, linac length and power requirement!

Conclusionso Maximum achievable average axial field for the TERA C-band structures is around 40

MV/m.(assumptions:– TW and SW are comparable– Modified Poynting vector and associated scaling laws validity– Pulse length scaling laws validity)

o High power tests of the C-band TERA prototypes are useful to:1) Check the validity of the scaling laws.

2) Increase the statistics of RF high power measurements at 5.7 GHz.

[TERA] Drive the choice of the most suited cell geometry for the CABOTO-C design.

o High-power test of the TERA 3 GHz single-cell cavity gains in importance:1) Comparison of structures in S, C and X-bands.

2) Validation of modified Poynting vector.

Conclusionso Maximum achievable average axial field for the TERA C-band structures is around 40

MV/m.(assumptions:– TW and SW are comparable– Modified Poynting vector and associated scaling laws validity– Pulse length scaling laws validity)

o High power tests of the C-band TERA prototypes are useful to:1) Check the validity of the scaling laws.

2) Increase the statistics of RF high power measurements at 5.7 GHz.

[TERA] Drive the choice of the most suited cell geometry for the CABOTO-C design.

o High-power test of the TERA 3 GHz single-cell cavity gains in importance:1) Comparison of structures in S, C and X-bands.

2) Validation of modified Poynting vector.

Conclusionso Maximum achievable average axial field for the TERA C-band structures is around 40

MV/m.(assumptions:– TW and SW are comparable– Modified Poynting vector and associated scaling laws validity– Pulse length scaling laws validity)

o High power tests of the C-band TERA prototypes are useful to:1) Check the validity of the scaling laws.

2) Increase the statistics of RF high power measurements at 5.7 GHz.

[TERA] Drive the choice of the most suited cell geometry for the CABOTO-C design.

o High-power test of the TERA 3 GHz single-cell cavity gains in importance:1) Comparison of structures in S, C and X-bands.

2) Validation of modified Poynting vector.

Thanks for your attention