September 4, 2008

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, FFAG’s, ….

– 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

September 4, 2008

FFAG08 Manchester Workshop – Dejan Trbojevic

1

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.



2

Introduction:

Hadron (proton, carbon, neutron) therapy machines today: synchrotrons, cyclotrons, FFAG’s, ….

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?



3

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 ( r

=

0.97 gr/cm 3 )

Kinetic Energy: 205.0 MeV/n

LET(in water): 0.4457 KeV/ m m



4

Experimental results from: NSRL Laboratory at Brookhaven National Lab - Adam Rusek

Ion: C 6+

Peak position: 8.375 cm in high density polyethylene ( r

=

0.97 gr/cm 3 )

Kinetic Energy: 200.2 MeV/n

LET(in water): 16.23 KeV/ m m



5

14.1 cm

8.21

2.6

-2.5

-6.9

-10.1

Orbit offsets and dimensions in the cell



6

The whole ring with all elements:

24 doublets

12 cavities

Three kickers

Circumference = 26.88 m

D=8.56 m r=4.278 m



7

Small proton therapy machine



8

Tunes vs. momentum

E k

=30.96 MeV



250.0 MeV

9

Betatron Functions Dependence on Momentum



10

L

BD

L

BF

G d

G f

B do

B fo

= 22 cm

= 30 cm

= -14.3 T/m

= 8.73 T/m

= 0.804 T

= 0.563 T

Minimum horizontal aperture:

A min

=0.140638+0.101838+6 s ~ 26 cm

Values of the magnetic fields at the maximum orbit offsets:

B d max-

B d max+

= 0.804 + (-14.3) * (-0.0484) = 1.496 T

= 0.804 + (-14.2) * (0.107) = -0.715 T

B

B f max+ f max-

Magnetic Properties:

= 0.563 + 8.73

= 0.563 + 8.73

* 0.141 = 1.794 T

* (0.102) = -0.327 T

Offsets at F d p/p x

0ff

(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

Offsets at D d p/p x

0ff

(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



11

Acceleration:

The total stored energy in the cavity is related to the amplitude of the RF voltage:

U



2 w r

V

2

RF

( R / Q ) angular resonant frequency is w r

Electron gains energy: eV

RF

( R / Q )



L / C

 w r

L



1 / w r

C



12

Acceleration:

26.88 meter circumference

22 MeV < proton kinetic energy < 250 MeV, 0.24 <  < 0.61

Central rf frequency = 374 MHz



13

Acceleration

Harmonic number variation



14

Requires a loaded quality factor Q=50

Full horizontal aperture 28 cm

Full vertical aperture 3 cm, R/Q = 33 Ohm (circuit) for beta=0.24

U



2 w

2

V accel

( R / r

Q )



15

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 Q=50 and fres=370 MHz the exponential decay time for the field is 43 nanoseconds. Two e-folding times is pretty good so

I’ll assume the voltage is limited by power

Can take about 20 kV of synchronous voltage.

P



V

2

/ 2 R , V



30 kV

nturns



250

MeV

-

28

MeV

20

kV

*

ncav



1 .

1



10

4

ncav



916



16

Accelerating cavity – Mike Blaskiewicz:

The voltage scales with beam velocity as

V (



)



E

0

 cos( 2

 z /



) dz cosh( z / a )



E

0 a

 cosh



 a





2





8



17

1

4

49

52

37

53

24 cells – twelve cavities 30 kV per cavity ~ 1300 turns: going through the third order resonance - horizontal phase space

102

400 900

55

150

500

1000

63

164

600

1100

73

200 700

1200

87

300 800

1340



18

1

15

420

507

24 cells – twelve cavities 30 kV per cavity ~ 1300 turns: going through the third order resonance - vertical phase space turn number

695 829 956 1187

704

733

857

88

6

1007

1138

1193

1200

618


807

916

1157


1300

19

Blow up from the third order resonance in x,x’

~1.3



20

Blow up from the third order resonance in y,y’

~1.9



21

5

7

2

3

1

24 cells – twelve cavities 30 kV per cavity ~ 1300 turns: going through the third order resonance - longitudinal phase space

10

30

55 90 600 1000

15

58

100

42 700

1100

18 61

200

47

400

800 1200

23 49 65

28 5

1

70 500

900 1300



22

Blow up from the third order resonance in long. space



23

3

0

40


10

20

1

24 cells – twelve cavities 30 kV per cavity ~ 1300 turns: third order resonance avoided , no random errors: x, x’ phase space

50 400

60

100

500

600

200

300

700

800


1200

1350

24

90

0

1000

1100

1

2

3

10


20

24 cells – twelve cavities 30 kV per cavity ~ 1300 turns: third order resonance avoided , no random errors: y, y’ phase space

200

500

900

1000

31 300

505

1109

53

401 694

1230

800

100

407

1300


25

3

4

1

2

5

6

24 cells – twelve cavities 30 kV per cavity ~ 1300 turns:

Third order resonance avoided , no random errors - longitudinal phase space

12 17

600 1000

7

13

18

700

1100

8

14

800

1200

15

9

96

900 1300

11

16 500



26

Blow up in x, x’ due to the random errors of 10 -3

1 third order avoided

506

2

731

35

941

1036


77

850

12395

12395/12=1032


27

Blow up in x, x’ due to the random errors of 10 -3

Third order avoided x o x f

/ x o

~1.8

Bmax~1.95 T @x=xmax f x



28

Blow up in y, y’ due to the random errors of 10 -3 third order avoided y o y f

/ y o

~1.4

o y’ y f y’ f



29

MOTIVATION

• Comparable (synchrotrons ~C=60m) 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:



30

Additional subjets:



31

Lattice got simplified with smaller number of magnets:



32

Basic cell of non-scaling FFAG small therapy accelerator



33

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



34

Orbits during acceleration and offsets in one cell

8.30 mm

-7.10 mm



35

Betatron Functions



36

Dimensions, Gradients and Magnetic Fileds

Kinetic energy range for protons: E min

= 1.35 MeV <-> E max

= 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:

QLF=0.17 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



37

Ring – circumference = 10.44 m, radius 1.66 m



38

Acceleration: same as for the proton therapy machine



39

September 4, 2008

nturns

MeV

MeV

kV

ncav

ncav

Small proton non-scaling FFAG accelerator for energy range of 1.35-12 MeV

• Orbits and offsets during acceleration.

• Magnets: Dimensions, gradients and fields

• Ring

• Acceleration

• Summary

Related documents

Products

Support

September 4, 2008

nturns

MeV

MeV

kV

ncav

ncav

Small proton non-scaling FFAG accelerator for energy range of 1.35-12 MeV

• Orbits and offsets during acceleration.

• Magnets: Dimensions, gradients and fields

• Ring

• Acceleration

• Summary

Related documents

Add this document to collection(s)

Add this document to saved

Suggest us how to improve StudyLib