Small proton therapy accelerator by non-scaling FFAG

1
Small proton therapy accelerator by non-scaling
FFAG
Dejan Trbojevic-BNL, Eberhard Keil-CERN, and
Andrew Sessler-LBL

• Introduction
• Proton/carbon therapy very fast growing field
  very large number of facilities.
• competition within proton therapy machines today
  synchrotrons, cyclotrons, FFAGs, .
• IBA, Siemens, Varian-ACCEL, Hitachi, Austron,
• Is there a reason to compete? price,
  circumference, fastest treatment rate,
  scanning-(treatment length), total ammount of
  steel
• Properties of the lattice
• Basic cell orbits
• radius, magnetic fields, aperture (orbit
  offsets), betatron functions, energy range,
  available drift space for cavities and
  exctraction/injection
• Acceleration
• Fast phase adjustments each turn- similar to the
  harmonic number jump.
• Results from the six dimensional tracking studies
• Concerns
• resonance crossing, fringe fields, emittance
  preservation, exctraction/injection, size of the
  RF power
• Summary

2
Introduction hadron therapy
From Steve Peggs PAC07 talk

• 1 in 3 Europeans will confront some form of
  cancer in their lifetime.
• Cancer is the 2nd most frequent cause of death.
• Hadron therapy protons, carbon, neutrons is 2nd
  only to surgery in its success rates.
• 45 of cancer cases can be treated, mainly by
  surgery and/or radiation therapy.

3
Introduction

• Hadron (proton, carbon, neutron) therapy machines
  today
• synchrotrons, cyclotrons, FFAGs, .
• Private companies producing them IBA, Siemens,
  Varian-ACCEL,
• Hitachi, .
• Are there reasons to get involved?
• Price might be to high?
• Size might be to large for a hospital?
  circumference, magnets?
• Rate for treatment could be faster?
• A total ammount of steel could be smaller?
• The energy and intensity modulation could be
  improved?

4
Experimental results from NSRL Laboratory at
Brookhaven National Lab - Adam Rusek
Very similar to the body cell density
Ion H Peak position 26.1 cm in high
density polyethylene (r0.97 gr/cm3) Kinetic
Energy 205.0 MeV/n LET(in water) 0.4457
KeV/mm
5
Experimental results from NSRL Laboratory at
Brookhaven National Lab - Adam Rusek
Ion C6 Peak position 8.375 cm in high
density polyethylene (r0.97 gr/cm3) Kinetic
Energy 200.2 MeV/n LET(in water) 16.23 KeV/mm
6
Orbit offsets and dimensions in the cell
L1.12 m
½ F
14.1 cm
D
½ F
8 cm
8.21
2.6
-2.5
-6.9
-10.1
38 cm
½ QLf44 cm/2
QLd22 cm
½ Ff ½ 0.15271631
Fd0.1090831
½ Ff ½ 0.15271631
7
The whole ring with all elements
24 doublets 12 cavities Three kickers Circumfere
nce 26.88 m
D8.56 m
r4.278 m
8
Small proton therapy machine
9
Tunes vs. momentum
Ek30.96 MeV
250.0 MeV
10
Betatron Functions Dependence on Momentum
11
Magnetic Properties
Offsets at F
dp/p x0ff(m) 50 0.140638 40
0.111097 30 0.082114 20 0.053819 10
0.026376 0 0.000000 -10 -0.025024
-20 -0.048317 -30 -0.069370 -40
-0.087506 -50 -0.101838
LBD 22 cm LBF 30 cm Gd -14.3 T/m Gf 8.73
T/m Bdo 0.804 T Bfo 0.563 T Values of the
magnetic fields at the maximum orbit offsets Bd
max- 0.804 (-14.3)(-0.0484) 1.496 T Bd
max 0.804 (-14.2)(0.107) -0.715 T Bf
max 0.563 8.73 0.141 1.794 T Bf max-
0.563 8.73 (-0.102) -0.327 T
Minimum horizontal aperture Amin0.1406380.1018
386s 26 cm
Offsets at D
dp/p x0ff(m) 50 0.107354 40
0.083583 30 0.060737 20 0.039014 10
0.018662 0 0.000000 -10 -0.016560
-20 -0.030484 -30 -0.041077 -40
-0.047447 -50 -0.048481
12
Acceleration
The total stored energy in the cavity is related
to the amplitude of the RF voltage angular
resonant frequency is wr
Electron gains energy
13
Acceleration

• 26.88 meter circumference
• 22 MeV lt proton kinetic energy lt 250 MeV, 0.24 lt
  ? lt 0.61
• Central rf frequency 374 MHz

14
Acceleration

• Harmonic number variation

15

• Requires a loaded quality factor Q50
• Full horizontal aperture 28 cm
• Full vertical aperture 3 cm, R/Q 33 Ohm
  (circuit) for beta0.24

16

• The cavity is about 1million.
• A 100 kW driver is about 1 million
• Imagine a bunch train that fills about half the
  ring at injection
• We have about 80 nanoseconds to change the cavity
  frequency when there is no beam (depends on
  energy)
• With Q50 and fres370 MHz the exponential decay
  time for the field is 43 nanoseconds. Two
  e-folding times is pretty good so Ill assume the
  voltage is limited by power
• Can take about 20 kV of synchronous voltage.

17
Accelerating cavity Mike Blaskiewicz
The voltage scales with beam velocity as
18
24 cells twelve cavities 30 kV per cavity
1300 turns going through the third order
resonance - horizontal phase space
1
400
900
53
102
4
500
150
55
1000
37
63
164
600
1100
73
49
200
700
1200
52
87
300
800
1340
19
24 cells twelve cavities 30 kV per cavity
1300 turns going through the third order
resonance - vertical phase space
956
1187
695
829
1
turn number
15
1193
857
704
1007
420
733
886
1200
1138
507
807
1157
618
916
1300
20
Blow up from the third order resonance in x,x
1.3
21
Blow up from the third order resonance in y,y
1.9
22
24 cells twelve cavities 30 kV per cavity
1300 turns going through the third order
resonance - longitudinal phase space
1
600
55
10
1000
90
30
58
2
15
100
700
42
1100
61
3
18
200
47
1200
800
400
5
65
23
49
7
28
51
70
500
1300
900
23
Blow up from the third order resonance in long.
space
24
24 cells twelve cavities 30 kV per cavity
1300 turns third order resonance avoided, no
random errors x, x phase space
900
400
1
50
60
1000
10
500
1100
100
20
600
1200
200
700
30
1350
800
300
40
25
24 cells twelve cavities 30 kV per cavity
1300 turns third order resonance avoided, no
random errors y, y phase space
900
1
20
200
500
1000
300
31
505
2
1109
401
694
53
3
1230
800
407
100
10
1300
26
24 cells twelve cavities 30 kV per cavity
1300 turns Third order resonance avoided, no
random errors - longitudinal phase space
1
12
6
17
1000
600
7
18
13
2
700
1100
19
14
46
8
3
800
1200
4
15
96
9
900
1300
500
5
16
11
27
Blow up in x, x due to the random errors of
10-3 third order avoided
12395/121032
28
Blow up in x, x due to the random errors of
10-3Third order avoided
xo
xf
xf /xo1.8
Bmax1.95 T _at_xxmax
29
Blow up in y, y due to the random errors of
10-3third order avoided
yo
yf
yo
yf
yf /yo1.4
30
MOTIVATION

• Comparable (synchrotrons C60m) or smaller size
  (cyclotrons are smaller but definitelly require
  large ammount of steel).
• Fast acceleration rate.
• Energy scanning simple single turn exctraction
  at required energy.
• No radiation loss (cyclotrons have unavoidable
  activation due to losses inside of cyclotrons as
  well as from the raster to allow the required
  energy range.
• Easy to operate because of the fixed and linear
  dependence of the magnetic field.
• Small orbit offsets small aperture.
• RESONANCE crossing
• End magnetic field effect
• Large power for the RF

CONCERNS

31
Additional subjets
32
Lattice got simplified with smaller number of
magnets
33
Basic cell of non-scaling FFAG small therapy
accelerator
34
Small proton non-scaling FFAG accelerator for
energy range of 1.35-12 MeV
Dejan Trbojevic and Sandro Rugierro

• Orbits and offsets during acceleration.
• Magnets Dimensions, gradients and fields
• Ring
• Acceleration
• Summary

35
Orbits during acceleration and offsets in one cell
25 cm
8.30 mm
Ek12 MeV
-7.10 mm
6 cm
Ek1.35 MeV
QLF/2 17/2 cm
BLD 10 cm
QLF/2
36
Betatron Functions
37
Dimensions, Gradients and Magnetic Fileds
Kinetic energy range for protons Emin 1.35
MeV lt-gt Emax 12 MeV Bending angles - both
magnets bend positive ANGBD
0.145444104332861 rad ANGBF
0.203621746066005 rad
Rigidity and central
momentum BRHO 0.334766674280 Tm
For dp/p-50
Bending fields in the Focusing and
Defocusing combuned function magnets
BYQ 0.400975145538842 T BYD
0.486898391011451 T
Gradients in
T/m GBF 8.70 T/m GBD-12.5 T/m
Dimensions QLF0.17 m BL 0.10 m Drift
between magnets 6 cm Drift for cavities and
kickers 25 cm. Maximum magnetic fields BF
max 0.401 8.70 0.083 1.25 T (12 kG )
BD max 0.4869 (-12.5) (-0.035) 0.95 T
38
Ring circumference 10.44 m, radius 1.66 m
r 1.66 m
39
Acceleration same as for the proton therapy
machine