Monte Carlo Simulation Study onMonte Carlo Simulation Study onCharge-deposition Distribution

f El t B E D t i tifor Electron Beam Energy Determination

길영미, 오영도1, 김상훈, 문성익, 조무현, 남궁원

포항공과대학교. 1포항가속기연구소

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Abstract

The electron energy is one of the principal parameters that gy p p pinfluence the depth-dose distribution and the depth-charge distribution within a material penetrated by the electron beams. To develop an easy-to-use device for measurement of the To develop an easy to use device for measurement of the electron beam energy, the Monte Carlo simulation is conducted on the depth-charge distribution in aluminum plates. The MCNPX 2 4 code is used for this simulation The aluminum plates consist 2.4 code is used for this simulation. The aluminum plates consist of 4 plates separated by air gaps. The thickness of each plate is determined for the collected charges to be sensitive to the l ct n b m n Th d pth ch dist ibuti ns und electron beam energy. The depth-charge distributions under

various beams energies and the consequent collected charges in each plate will be used for determining the electron beam

f h l denergy from the experimental data.

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Condition of MCNP Simulation

Al plates

Mono-energetic or Gaussian Electron Beam

0.07

0.08

0.0950 MeV (σ=1 MeV)50 MeV (σ=2 MeV)50 MeV(σ=3 MeV)

0 03

0.04

0.05

0.06

Frac

tion

50 MeV (σ 3 MeV)50 MeV (σ=4 MeV)50 MeV (σ=10 MeV)

0.5 cm15 cm

0.00

0.01

0.02

0.03

20 30 40 50 60 70 80 Electron 20 30 40 50 60 70 80

Energy (MeV)

Electron Charge

Deposition

Assuming that the beam energy distribution

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g gyis the gaussian distribution.

Electron Charge Deposition Distribution

0.12

0.14

n cm

2 /g)

8.0 MeV

8.5 MeV

9.0 MeV

9.5 MeV1.0

1.2

cm2 /g

)

0.06

0.08

0.10

Dep

ositi

on (F

ract

ion

10.0 MeV

10.5 MeV

11.0 MeV

11.5 MeV

12.0 MeV 0.4

0.6

0.8

Dep

ositi

on (F

ract

ion

c

8.0 MeV

8.5 MeV

9.0 MeV

0.02

0.04

Elec

tron

Char

ge D 12.0 MeV

0.0

0.2

0.4

Elec

tron

Char

ge D 9.5 MeV

10.0 MeV

10.5 MeV

11.0 MeV

11.5 MeV0.00

0 1 2 3 4 5 6 7 8

Mass Thickness (g/cm2)

-0.20 1 2 3 4 5 6 7 8

Mass Thickness (g/cm2)

12.0 MeV

• Differential charge-deposition distribution in aluminum for mono-

• Integral charge-deposition distribution in aluminum for mono-energetic beams of 8.0,

Integrated

energetic beams of 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, and 12.0 MeV.

• The y-axis represents normalized charge collected by a unit thickness of aluminum

g8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, and 12.0 MeV.

• This curves will be compared with the experimental data

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collected by a unit thickness of aluminum plate per unit incident electron.

experimental data.

Effect of Energy Spread

1.2

2 /g)

0.8

1.0

n (F

ract

ion

cm

0 2

0.4

0.6ar

ge D

epos

itio

50 MeV (mono)50 MeV (σ=1 MeV)50 MeV (σ=2 MeV)

-0.2

0.0

0.2

Elec

tron

Cha 50 MeV (σ=2 MeV)

50 MeV (σ=3 MeV)50 MeV (σ=4 MeV)50 MeV (σ=10 MeV)

0 5 10 15 20 25 30 35

Mass Thickness (g/cm2)

• Integral charge deposition distribution in aluminum for electron beams with mono-energy, σ=1 MeV, σ=2 MeV, σ=3 MeV, σ=4 MeV, and σ=10 MeV.

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σ 3 MeV, σ 4 MeV, and σ 10 MeV.

Experimental Condition of Test Linac at PAL

Cathode Temp. Controller (RS232)

Cathode Heater PS (RS422)

RF-gun

GQ1

BPRM#3

GQ1GQ2

GST1_ H/V

Alpha Magnet

GST2 H/VBCM 1

A/C1 A/C2

ST1-H ST1-V

QT1_S QT1_L

BCM 2 BCM 3

QF1 BAS

p g e

GQ3 GQ4

BPRM#1PGV#1

A/C1 A/C2

Solenoid 1-17 BPRM#2 ST2-H ST2-V PGV#1

QD2

BAS_BPRM6.4 m

1010 m

13.5 m

16 m

S ifi ti f T t liSpecification of Test linac- Electron accelerator- Maximum energy: 100 MeV- Beam current: 30 mA

M i titi t 10 H

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- Maximum repetition rate: 10 Hz- Pulse width: 1.6 μs.

Experimental Setup

Electron Beam of 50, 55, and 60 MeV

2.13 13.674.87 2.14

,

16 54

Unit: cm16.54 2.49 2.97 7.55

Ch.1

Ch.2

C1/(C1+C2+C3+C4)

(C1+C2)/(C1+C2+C3+C4)Integral charge deposition in each depth

Ch.3

Ch.4(C1+C2+C3)/(C1+C2+C3+C4)

p

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BCM & Charge Deposition Measurement at Test Linac

Gun forward

Gun reflect

BCM 2

BCM 3

50 MeVBCM 50 MeV

Specification of Electron Beam

BCM

Specification of Electron Beam

Energy 50 MeV 55 MeV 60 MeV

Current 7.6 mA 12.4 mA 15.6 mA

Repetition rate 6 Hz

Pulse width 1.6 μs

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60 MeV

Comparison Measurement with Calculated Data

1.0

1.2

Frac

tion)

Charge Loss = Charge Deposition

0.6

0.8

ge D

epos

ition

(F Charge Loss = Charge Deposition

0.2

0.4

al E

lect

ron

Char

50 MeV (calculated)

55 MeV (calculated)

60 MeV (calculated)

50 MeV (measurement)h h

-0.2

0.0

0 2 4 6 8 10 12

Inte

gra 50 MeV (measurement)

55 MeV (measurement)

60 MeV (measurement)

Charge Loss > Charge Deposition

Thickness (cm)

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Conclusion

• The Monte Carlo simulation is conducted on the charge-gdeposition distribution in aluminum plates to develop an easy-to-use device for measurement of the electron beam energybeam energy.

• We have measured the charges collected in Al plates for 50, 55, and 60 MeV electron beams using test linac at PAL.

• The measured data in this study are in agreement with the MCNP simulation within 3 % differencethe MCNP simulation within 3 % difference.

• Further study; search for analytic fitting function for the beam energy identification.

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