drabrh lecture on klystron

8/9/2019 Drabrh Lecture on Klystron

1/23

E-Linac Initiative: New ElectronDriver for RIB Science

Design for MW SC linear accelerator driver for

independent photo-fission production of RIBs

Shane Koscielniak, TRIUMF Accelerator PhysicistU. Victoria, 06 March 2009

CANADAS NATIONAL LABORATORY FOR PARTICLE AND NUCLEAR PHYSICSOwned and operated as a joint venture by a consortium of Canadian universities via a

contribution through the National Research Council Canada

LABORATOIRE NATIONAL CANADIEN POUR LA RECHERCHE EN PHYSIQUE NUCLAIRE ET EN PHYSIQUE DES PARTICULES

Proprit dun consortium duniversits canadiennes, gr en co-entreprise partir dune

contribution administre par le Conseil national de recherches Canada


2/23

Elinac Initiative - Electron Driver for RIB 2

E-linac Talk Outline

Introduction Motivation/Impacts

Performance milestones

E-linac Specification

Superconducting RF Because

Relation to TESLA/ILC ILC: voltage-gradient limited design

E-linac: power-gradient limited design Baseline design

High Power RF building blocks (2 slides)

Layout functional & flexible

Capitalize on existing equipment designs

Activity in support of design effort (3 slides)

Summary


3/23


New Science: Nuclear physics with neutron-rich RIBs, and9Be(,p)8Li for -NMR studies in Materials and Molecular Sciences.

Complementary & independent driver for RIB production.

Implements strategy of multiple beams (e, p) to multiple users toaccelerate science output.

E-Linac will operate through annual cyclotron shutdowns

providing strong year-round RIB experimental program.

Leverages valuable existing infrastructure:

Proton Hall, shielded vault with services

World-class RIB experimental apparatus (detectors)

Builds further SCRF expertise base from

(1, 100 MHz, 4K) to (=1, 1 GHz, 2K) -=v/c relativistic speed

Prepares Canada for SCRF projects world-wide (ILC, CERN-SPL)

Qualifies commercial partner (PAVAC) to build SCRF cavities.

E-Linac Motivation/Impact


4/23


What is photo fission?

Electron

beamTungsten

convertor

-rayphotons Multilayer Uraniumoxide, or carbide

production target

Radioactive ions diffuse

out, are ionized, mass-

separated, accelerated

Production efficiency high: one -

photon for three electrons (30 MeV)

Photo-fission cross-section high for 15

MeV due to Giant Dipole Resonance

target


5/23


Beam power (MW) 0.5

Duty Factor 100%

Average current (mA) 10

Kinetic energy (MeV) 50

E-Linac Specification

Photo-fission productsdistribution using 50 MeV 10 mA

electrons on to Hg convertor &

UCx target

Number of photo-fission /second

versus electron energy for 100 kW

e-beam on Ta convertor and U target.


6/23


The requirement:50 MeV 10 mA

= MW beam

power eliminated

on target.

Bunch charge (pC) 16

Bunch repetition rate (GHz) 0.65

Radio frequency (GHz) 1.3

Average current (mA) 10

Kinetic energy (MeV) 50

Beam power (MW) 0.5

Duty Factor 100%

E-Linac Beam Specification

Bunch vital statistics (rms) inject eject


7/23


High duty factor or continuous operation is inconceivable with NC

cavities for 50 MeV, need 4-8 MW wall-plug power.

With SC cavities need 1.5 MW wall-plug power

- enormous operational cost savings!

We chose Superconducting RF because:

1.3 GHz @ 2 K is

cost minimum

Cost scales as Power/Length@ constant gradient =


8/23


Enormous world-wide effort in this regime since the 1990s dedicated to

TESLA at DESY and now to International Linear Collider (ILC).

The Tesla Technology Collaboration (TTC) exists to promote, share

and disseminate the remarkable results of the effort.

With major impetus from TESLA, technology is now mature withgradients >20 MV/m routine.

Projects now include: DESY X-ray FEL, Cornell Energy Recovery Linac

(ERL), Daresbury ERL Prototype, KEK-Free Electron Laser (FEL). KEKand FNAL efforts for ILC, Jefferson Lab upgrade, TRIUMF e-linac, etc.

TRIUMF joined TTC in April 2007.

We chose 1.3 GHz, 2K technology because:

1.3 GHz SCRF cavities have been in development for >30 years,starting with 27 m long 50 MeV SCA at Stanford.


9/23


DESY single-cell and 9-cell cavities form starting point for many

SCRF linac designs around the world

ILC cavity module

Commonality of ILC with Fission Driver stops here and does not

extend to the cryomodule or High Power RF


10/23


9 mA, 333 MeV energy gain

3 MW beam power/cryomodule

BUT ILC not c.w.

1 ms pulse, 5 Hz9 cavity/cryomodule; 9 cell/cavity

300 kW/cavity (peak power)

Average current

0.04 mA

Single input coupler per cavity;31 MV/m gradient

Average power 16kW/cavity

2 HOM coupler/cavity Duty factor 0.5%

ILC Main Linac cryomodule = 9 cavities

poster boy for high-gradient, low average power

But photo-fission driver will operate continuous wave (c.w.)


11/23


ILC input coupler:

16kW average power

Fission Driver: 500 kW CW RF power has to propagate

through input couplers and cavities to beam

E-linac input coupler:

60kW average power

Cornell/CPI-Eimac

E-linac: design driven by challenges of 100% duty factor

high-power CW input coupler & limited choice of klystrons 2 kelvin heat loads in CW operation

Linear Collider:

duty factor = 0.5%,design is limited by accelerating gradient (31.5 MV/m)


12/23


130 kW klystron

50 kW coupler

50 kW coupler

Beamcurrent

Cavitygradient

# cavities Beam energy Beam power

300 kW

10 mA 10 MV/m 5 50 MeV 500 kW

20 mA 5 MV/m 10 50 MeV 1 MW

5 mA 20 MV/m 3 60 MeV

HP RF building block

for e-linac

E-linac RF unit =

100 kW/cavity


13/23


e-GUN

BUNCHERCAVITY

BEAM

TRANSPORT

LINE

50 kW 50 kW

MAIN LINAC

CRYOMODULE #1

25 kW

INJECTOR

LINAC

e-GUN

BUNCHER

CAVITY

BEAM

TRANSPORT

LINE

50 kW 50 kW 50 kW

50 kW 50 kW 50 kW

50 kW

50 kW

MAIN LINAC

CRYOMODULE #2MAIN LINAC

CRYOMODULE #1

50 kW

50 kW

INJECTOR

LINAC

One 130 kW

klystron/cavity

E-linac in 2010-2015 plan

100 kW, 25 MeV

E-linac in 2015-2020 plan

500 kW, 50 MeVE linac power distribution


14/23


CW operation has other challenges:

Higher heat load in all RF components: cavity, input coupler,HOM coupler/absorber, etc

Limited choice of c.w. klystrons, c.w. couplers

Fission driver,10 MV/m

4 cavity

ERL20 MV/m

4 cavity

TESLA TDR23.4 MV/m

12 cavity

RF Load (W) 41.6 166.4 4.95

2K Sum (W) 44.4 251.5 9.05

5K Sum (W) 29.1 34.5 15.94

Input Couplers 713 265 80.9

80K Sum (W) 717.6 601.2 183.02

2K & 80K sums almost 4 TESLA values

Beam powerrelated


15/23


E-Linac Baseline Layout

Thermionic gun: triode; 100 keV; 650 MHz

Injector linac

10 MV/m, Q=1010

10 mA, 5-10 MeV gain

100 kW beam pwr

Two cryomodulesTwo 9-cell cavities/module,

10 MV/m, Q=1010

10 mA, 40 MeV gain

400 kW beam pwr

NC buncher

SRF Injector

Main linac

Focusing & diagnostic packages

Division into injector & main linacs allows:

Possible expansion path to test-bed forEnergy Recovery Linac (ERL) e.g. 10 mA, 80 MeV

Recirculating Linear Accelerator (RLA) e.g. 2 mA, 160 MeV

(acceleration & additional bunching)

Module #1 Module #2


16/23


Bunch length 24 ps

Relative

energy

spread

0.7%

Output at 50 MeV

from injector with

2 single cell =1cavities in

capture section


17/23


DC gunbunchercryomodule

beam dump

beam lines

Cornell ERL Injector serves as

model for many components

The path-finders for c.w. high-power, high-current linacs are

the Energy Recovery Linac (ERL) based light-sources,

particularly their injector linacs (no energy recovery)

of fission driver


18/23


Use/adapt existing equipment designs wherever possible

TTF/ILC 9-cell cavities

Cornell/CPI 50 kW c.w. power couplers variant of ILC/Orsay coaxial couplers

- Tested > 60 kW

klystrons from e2V or CPI/Eimac?

XFEL-type ceramic HOM absorbers

C W Cryomodules


19/23


Changes compared to TTF cryomodule:

Increase diameter of 2-phase 2 K He pipe for

c.w. cavity operation

Direct gas cooling of chosen 5 K and 80 K

intercept points with He-gas flow

HOM absorbers between cavities

Tuner stepper easily replaceable

In-situ bake for input couplers

Frontier c.w. for high duty or high-power, high-current linacs are driversfor FELs - particularly injector linacs for Energy Recovery Linacs

Cornell ERL Injector forms existence proof for -MW capable

cryomodule forms reference model for E-Linac design

C.W. Cryomodules

ILC ariant of Sacla


20/23


ILC variant of Saclay

lever/lateral tunerOr INFN

blade/coaxial tuner?Tuner: Costing based on

INFN blade/coaxial tuner.XFEL industrialisation

makes Saclay/lateral

tuner a strong candidate.

Two candidates for NC single-cell

1.3 GHz buncher cavity

Daresbury

EMMA FFAG

Rossendorf Cavity: Rshunt1.2 M, Q 1.4E4


21/23


NIST/JLab electron gun donated to

TRIUMF e-gun development station.Will convert from diode to triode.

Vacuum pumps and HV power supplies

on order.

Emittance depends strongly on cathodesize, geometry, peak current, etc

Need beam characterization effort.

ILC: Photonic gun expensive, high maintenance, 10-11 torrFission driver: Thermionic gun inexpensive, low maintenance,

pressure not critical (10-9 torr).

RF modulated gun avoids chopping and 3 kW beam dumpat start of linac.

Electron Source


22/23


Summary

E-Linac is central component of the TRIUMF 10-year vision.

The fission driver represents a major new RIB source provides

complementarity to proton-driven RIB production.

Suite of potential RIB applications

Nuclear/astro physics

Materials & molecular sciences

Life/medical sciences

Light source technology test bed

L-band SCRF technology provides cost effective approach toMW-class fission driver and capitalizes on world-wide R&D

There are cell, cavity, input coupler, HOM damper, tuner,

klystron, IOT, cryostat and BPM designs all pre-existing

eliminates substantial R&D & cost.

Participate in ILC and other SRF projects world wide, e.g. SPL

E-Linac is well-matched to the scale of the TRIUMF facility and

its accelerator expertise.


23/23


A brighter future? light source with photocathode and high-

voltage gun

Study compatibility of light source (e.g. IR FEL or Compton Source)

beam parameters with e-linac design

Final parameters at user:

Bunch charge: 100 pC

Bunch length r.m.s. 1 ps (approx 4 ps FW)

Bunch emittance r.m.s. N 10 m

Bunch repetition rate up to 100 MHz

Gun type: photo-cathode (DC or RF? TBA)Gun voltage: TBA

drabrh lecture on klystron

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