BBd/2008 1

Klystron

BBd/2008 2

BBd/2008 3

Magnetron

BBd/2008 4

Magnetron

BBd/2008 5

Magnetron

Resonansfrekvens ca 3 GHz

BBd/2008 6

Automatisk frekvensreglering (AFC)

Magnetron

Motor

S/H

Frequency selection

Wave-guide

Cavities

PRF

Water of constant temperature

BBd/2008 7

Magnetron

Magnetspole

S/H

PRF

Phase adjuster

Hybrid coupler

Tuning probe drive

Frequency selector

Automatisk frekvensreglering (AFC)

BBd/2008 8

Gun

BBd/2008 9

Spänning Tid

4μs

2.5ms

50kV

+10V

Elekta

Gun

BBd/2008 10

Magnet

Honeycomb anode

Catode plate

Catode plate

Magnet

Slotted cathode

Vakuumpump

BBd/2008 11

An ion pump (also referred to as a sputter ion pump) is a type of vacuum pump capable of reaching up to 10−11 mbar under ideal conditions.[1] An ion pump ionizes gases and employs a strong electrical potential, typically 3kV to 7kV, to accelerate them into a solid electrode. A swirling cloud of electrons produced in hollow ionizes incoming gas atoms and molecules while they are trapped in a strong magnetic field. The swirling ions strike the chemically active cathode inducing sputter and are then pumped by chemisorption which effectively removes them from the vacuum chamber, resulting a net pumping action. Inert and lighter gases, such as He and H2 do not effectively induce sputter and are absorbed by physisorption. Some fraction of the energetic gas ions (including gas that is not chemically active with the cathode material) that strike the metal cathode steal an electron from the surface and rebound as a neutral atom. These energetic neutrals are reflected back from the cathodes and buried as neutrals in exposed pump surfaces.[

BBd/2008 12

+ - -

Vågens fashastighet = 1/(LC)-1 = elektronernas hastighet = 0.4c

Vågens fashastighet = elektronernas hastighet ≈ c

Massa

Tid

C

L

- - - - - - - - -

Bunching

BBd/2008 13

+

-

+ -

+

Gantry rotation

2R-coils

2T-coils

Power amplifiers Adjusted for flat field in

G-T direction

Adjusted for flat field in A-B direction

-

Styrning av elektronstråle 1

BBd/2008 14

PRF

PRF

S/H

+ -

2R-coil

Auto

Manual

Power amplifier

+ - Adjusted for flat field in G-T-direction

Ionisation chamber

*

*

Styrning av elektronstråle 2

BBd/2008 15

Styrning av elektronstråle 3

PRF

PRF

S/H

2R-coil

Power amplifier

Ionisation chamber

ADC Computer program DAC

*

*

BBd/2008 16

F1 F2

e-

e-

θ

x x Icke-optimala B-fält

Fokusering

BBd/2008 17

t1 + +

+ +

+ +

- -

- -

- -

t2 + +

+ +

- -

- -

- -

+ +

”Traveling wave”-acceleratorrör

E-fält e-

BBd/2008 18

e-

”Traveling wave”-acceleratorrör

BBd/2008 19

t1 + +

+ +

+ +

- -

- -

t2 + +

+ +

- -

- -

- -

+ +

E-fält e-

”Standing wave”-acceleratorrör

- -

BBd/2008 20

t1 + +

+ +

- -

- - E-fält

e-

”Standing wave”-acceleratorrör

t2 + + + +

+ - -

- E-fält

- -

+ +

-

+ + + + -

- -

BBd/2008 21

”Standing wave”-acceleratorrör

BBd/2008 22

Jämförelse mellan traveling –och standing wave accelerator

Struktur: Krav på strukturen (ytan):

Resonant struktur: Pris:

Diameter: Längd:

Antal celler/våglängd: Shuntimpedans: Kopplingsfaktor:

Maximal elektronström: Elektrisk fältstyrka:

Anslutning av mikrovågorna: Känslighet för frekvensvariationer:

Känslighet för fasvariationer: Beamloading effekten:

Vacuumkrav:

Traveling wave Standing wave Enkel Viktig Normal Normal Liten Lång Ca 3 50-75MΩ/m Liten Ca 2A Låg Vid GUN Liten Liten Låg Låg

Komplex Mycket viktig Mycket Dyr Stor Kort 2 Ca 100MΩ/m Stor Ca 0.5A Stor Längs strukturen Stor Stor Hög Hög

BBd/2008 23

1. Modulator 2. Gun 3. Magnetron eller klystron 4. Frekvensstyrning 5. Cirkulator 6. Acceleratorrör 7. Fokusering 8. Styrning av elektronstrålen 9. Vakuumpump 10. Last 11. Energistyrning 12. Böjmagnet 13. Target och elektronfönster 14. Spridningsfolier 15. Primärkollimator 16. Utjämningsfilter 17. Jonisationskammare 18. Kil 19. Speglar 20.MLC

21.Bländare 22.Strålhuvud 23. PRF-generator 24.Svavelhexaflourid 25 Kylsystem 26.Interlock-system 27.Dosimetrisystem

BBd/2008 24

⇒

Ökad elektronström

Reduktion av elektrisk fält p.g.a. överföring av energi till elektroner

(energibevarande)

⇒ Reduktion av elektriskt fält

⇒ Reduktion av elektronenergien ⇒ Reduktion av fotonenergin

⇒

Beam loading

BBd/2008 25

PRF

PRF

S/H

+ -

Auto

Manual

Power amplifier

+ - Adjusted for correct energy

Ionisation chamber

Pulse transformer

Gun

High voltage

*

*

Energistyrning 1

BBd/2008 26

Energistyrning 2

PRF

PRF

S/H

Power amplifier

Ionisation chamber

ADC Computer program DAC

Pulse transformer

High voltage

Gun

*

BBd/2008 27

Energistyrning 3

PRF

PRF

S/H

Power amplifier

ADC Computer program DAC

Pulse transformer

High voltage

Gun

Slits

e-

”Slalom” bending magnet

*

*