Waldur Symposium 2006 ‘Pulsed Power’

Pulsed DC Acceleration

Seth Brussaard

Outline

Accelerators

The Future of Accelerators

Pulsed DC Acceleration

CERN

Accelerators

10 keV

CRT

10 MeV

Cyclotron

10 GeV

Synchrotron Collider

10 TeV

Supernova

Future Accelerators

ILC: International Linear Collider

XFEL: X-ray Free Electron Laser

ILC: International Linear ColliderP.Grannis, Michigan State

ILC

ILC: International Linear Collider

9- March-06 LCWS06 Bangalore 21

Superconducting RF Cavities

High Gradient Accelerator35 MV/meter -- 40 km linear collider

XFEL: X-Ray Laser

XFEL: X-Ray Laser

Scaling Laws

Higher Energy

Smaller Details

Larger Accelerator

More €

More (Pulsed) Power

Shorter Pulses

Better time resolution

New Accelerator Concepts

More Research

Higher Peak Current

Challenges for Future Accelerators

Shorter Bunches

with

More Electrons

Brightness

FCoulomb FCoulomb

ce-FLorentz

low Energy relativistic Energy

femtosecondLaser

Getting to the speed of light fast

Electron Rest Mass: 0.511 MeV

Accelerate to a few MeV

over a short distance

Total power 10 MWFrequency 2998 MHzQ (2×) 7200

TU/e Photoinjector

Maximum output energy: 6.9 MeVCathode field at max energy: <100 MV/mLaunch phase: –50°

norm

aliz

ed fi

eld

position (cm)0 105 15

0

1

Getting to the speed of light fast

Electron Rest Mass: 0.511 MeV

Accelerate to a few MeV

over a shorter distance

Breakdown

Breakdown needs time

10-9

10-7

10-5

10-3

108 109 1010

td

E V/m

s

A. Emelyanov

Pulsed DC Acceleration

Make MegaVolt pulses

that are shorter than 1 nanosecond

Megavolt Pulser

Megavolt Pulser

Pulse Forming Line

Pulse Forming Line

0 400 800t [ ns ]

U [M

V]0

24

0-2

40 42 44 46 48 50

1

40 42 44 46 48 50-2

-1

0

2

t [ns]

U [

MV

]

Vacuum Diode

Cathode Anode

3.5 MV pulses3 mm Acceleration Gap

> 1 GV/m

Jitter

1.5 2.50

Output Voltage[ MV ]

coun

ts

1.5 2.5

20

40

60

2.52.0time (ns)

300 600400 5000

coun

ts

10

20

30

☺ Fast (ps rise time)

☺ Almost no time jitter

No recovery after breakdown

Limited to ‘low’ power

☺ High voltages, high currents

☺ Good recovery after breakdown

Slow (sub-ns rise time)

Large time jitter due to stochastic breakdown processesspark gap

coax

trigger laser

Semiconductor switch vs laser triggered spark gap

Photoconductive switching of a spark gap

☺ High voltages, high currents

☺ Fast switching by fs laser (ps rise time)

☺ Almost no jitter (no stochastic breakdown processes)

Ionization of the complete gap with high power fs laser

spark gapcoax

TeraWatt switching laser

Photoconductive switching spark gap setup

Brass (inner Ø 15 mm)Cu (Ø 6 mm)

Probing beam

TW switching beam2 MV,

1 ns pulse

Switched pulse with ps risetime

switched pulses @ different laser energies

-40 -20 0 20 40

time (ps)

num

bero

f sho

ts

15k

10k

5k

0

jitter: σ = 12 ps

Summary of Results

• 2 MV, 1 ns pulses produced by Tesla Transformer with Pulse Forming Line

• Jitter 20-70 ns

• Photoconductive Spark Gap Switch demonstrated at 5 kV

• Jitter < 10-15 ps

‘Artistic’ impression of a multistage accelerator

2 MV, 1 ns pulse

Laser trigger

Accelerator structure

Electron bunch

Spark-gaps

25 mm

< 10 psswitching time

GV/m 3 MV

3 mm between plates

plate thickness about 3 mm

Conclusions

For Future Accelerators:

More Pulsed Power

Better Pulsed Power