International Particle Accelerator Conference6th

May 3-8, 2015 Richmond, VA, USA

STATUS OF THE TOP-IMPLART PROTON LINACP. Nenzi1, F. Ambrosini3, A. Ampollini1, G. Bazzano1, F. Marracino1,

L. Picardi1, C. Ronsivalle1, C. Snels2, V. Surrenti1, M. Vadrucci1

1ENEA Frascati Research Center, Frascati, Italy, 2ENEA Casaccia, Roma, Italy, 3Università «La Sapienza», Roma, Italy

AbstractIn this work we present the latest update on the construction of the TOP-IMPLART proton LINAC at the ENEA C.R. Frascati Accelerators Laboratory. TOP- IMPLART is a 150 MeV proton accelerator for protontherapy applications funded by Regione Lazio (Italy). We have successfully commissioned the first 3GHz LINAC structure reaching the energy of 11.6 MeV (from 7 MeV), demonstrating the first proton acceleration in a SCDTL structures at this energy. The second SCDTL LINAC has been tuned and brazed and in delivery to the installation site, the third one is under construction.

SCDTL-1

Conclusion: The medium energy section of the TOP-IMPLART accelerator is under construction at the ENEA Frascati. The first two structures have been completed. The first one is routinely used for experimentation. The second one is going to be delivered for installation and commissioning. The third structure has been simulated and the drawings are under finalization. The design of the fourth structure will start soon.

SCDTL-2 SCDTL-3

The TOP-IMPLART LINACat ENEA-Frascati

Experimental vertical line

7 MeV Injector: Hitachi-AccSys PL7 Model

MEDIUM ENERGY PART (7-35 MeV)

under development

0

5

10

15

20

25

30

35

40

45

100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850

Trans

mitte

d cur

rent

(m

A)

Aluminium thickness (mA)

measurements RF off

measurements RF on

SRIM 11.63 MeV

SRIM 7 MeV

0

20

40

60

80

100

120

0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6

Acce

lera

ted

char

ge n

orm

aliz

ed

to m

axim

um v

alue

(%)

Power (MW)

Simulation

Measurements

Computed energy spectrum at SCDTL-1 exit

Energy measurement from range in Aluminium

Transmitted charge after 700 µm Al vs RF Power

Behaviour under pulse operation

0 0.2 0.4 0.6 0.8 12.96

2.97

2.98

2.99

3

3.01

3.02

3.03

3.04

phi (pi units)

Fre

quen

cy(G

Hz)

SCDTL Module 3

w1(GHz)= 3.00574

w2(GHz)= 2.99380

k= 0.01933

k1= -0.00649k2= 0.00257

Stop Band(GHz)= 0.00162

The TOP-IMPLART (Intensity Modulated Proton Linear Accelerator for RadioTherapy) accelerator is a proton LINAC designed for medical applications. The accelerator, when completed, will deliver a proton beam with energy variable in the 85 MeV to 150MeV range. TOP-IMPLART accelerator consists of: a commercial injector (up to 7 MeV), the PL7 model produced by Hitachi-AccSys (425 MHz, 100 μs pulse, 100 Hz pulse repetition frequency, maximum), a medium energy section (7 MeV to 35 MeV), consisting of 4 SCDTL structures (2997.92 MHz, 4 μs pulse), a high- energy section (35 MeV to 150 MeV), consisting of 12 CCL structures (2997.92 MHz, 4 μs pulse). The injector section is connected to the first SCTDL structure by a LEBT consisting of a first quadrupole doublet followed by a deflecting magnet and a second quadrupole doublet. The LEBT is meant to focus the beam to fit the SCDTL pipe that has 4 mm diameter, whereas the injector pipe is 35mm diameter. The deflecting magnet is used to deliver the proton beam to a vertical beam-line used in radiobiology experiments.

Low Energy Beam Transfer Line with the vertical line in the middle

The SCDTL based medium energy section is actually driven by a TH2090 15MW klystron tube installed in a pulse forming network modulator. Klystron RF signal is generated by a DDS unit and amplified by an AM10 solid state power amplifier.

The system will be upgraded with a TH2157A (10MW) klystron and a solid state modulator to improve pulse to pulse amplitude variability (<0.1%).

Parameter Value

Length 1.1 m

# of tanks 9

# cells/tanks 4

RF power 1.3 MW

Status Operation

Parameter Value

Length 1.1 m

# of tanks 7

# cells/tanks 5

RF power 1.6 MW

Status Tuning

Smith Chart (measured) showing the overcoupling of the structure. The value of β=1 can be obtained on the fully brazed structure by adding stubs in the RF feed. This procedure allows to compensate changes that may occur during the finalization of the structure.

Resonance modes of the SCDTL-2 structure excited from the central tank (in reflection).

Parameter Value

Length 1.35 m# of tanks 5# cells/tanks 6RF power 2 MW

StatusUnder

constructionInstallation is foreseen in September 2015

Modal dispersion of SCDTL-3

Computed longitudinal electric field on axis in the π/2 mode ( 2998.5 MHz, E0=15.62 MV/m).

Numerical calculations highlight that, with increase of tanks length, higher order modes move towards the operation band. In particular this is true for the transverse mode TE111, which is directed in the orthogonal direction to the stem axis. To move this mode away from the operation band, post couplers are required in the two final tanks.

3000

3020

3040

3060

3080

3100

3120

3140

115 120 125 130 135 140 145

MHz

Tank length(mm)

Modo fondamentale (TM010)

Primo modo superiore

Fundamental mode

First higher order mode

2700

2750

2800

2850

2900

2950

3000

3050

0 0.5 1 1.5 2 2.5

Freq

uenz

a m

odi T

E (M

Hz)

penetrazione post (cm)Post penetration (cm)

TE m

odes

freq

uenc

y (M

Hz)

Frequencies of the fundamental and first higher order mode at increasing tank length.

Post penetration into the cavity moves away the frequency of the TE higher orders modes from the operation band.