Leitner

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y

NSCL/FRIB Laboratory

Michigan State University

D. Leitner, July 2013, Slide 1

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Accelerators

Accelerators Applications

Accelerators are designed and optimized for the science goalsstudied at the facility

,

particles: rare isotopes, neutrinos, neutrons, x-rays),postaccelerators.. Electrostatic: Pelletrons Cockcroft Walton Generators Hi h volta e latforms

Electromagnetic: Cyclotrons, Linear Accelerator, Synchrotron, + storage rings

Main Parameters

Particle type and range (electrons, protons, heavy ions, rare isotopes)

Intensity or Beam Power

e.g. FRIB: 200MeV/u for Uranium, 8.4pA

heavy ions 16O-238U for fragmentation (+lighter ion option)

particles /sec = dN/dt = I/Qe (1 pA == 6x1012 /s)


Power= dN/dt [pA] x Particle Energy [MeV]= 200*8.4*238=400kW

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Accelerators

Applications of Accelerators in Nuclear Physics [1]

10 Low Energy Nuclear Physics

Accelerators are tailored to the experiments they support

O-ignition

Ne-ignition

Si-ignition

C-ignition9

ec ros a c cce era ors: ew e ew

MeV (total energy) Extremely low energy accelerators (aimed

to measure solar fusion cross sections),

log

(T

c)

He-ignition

8

,

Low energy accelerator, stable beams(e.g. Notre Dame), electrostatic

accelerators, < 5MeV

H-

ignition

Cyclotrons, linacs, SC-Linacs, :>100keV/nuc tens of MeV/nuc

Stable Beam Facilities (Atlas, 88-Inch,

log (c)0 42 8 104 6

..

Radioactive Ion Beam postaccelerators(Rex-Isolde, ISAC, ReA, CARIBU..)


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Rare Isotope Beam Production

Techniques Target spallation and fragmentation by light ions (ISOL Isotope separationon line)

beamTarget/Ion Source

PostPost

Photon or particle induced fission

AccelerationAcceleration

Neutrons Uranium Fission

PostPost

AccelerationAcceleration

Reactor

ProtonsAcceleratorElectrons

n- g t eparat on o ow ng nuc eon trans er, us on, pro ect e

fragmentation/fissionbeam

Accelerator

targetFragment Separator

Beams used without stopping

PostPost


Gas catcher/ solid catcher + ion source

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Exotic Beams Produced in Flight at NSCLs CCFExperienced group of PhD beam physicists delivers rare isotope beams to users

More than 1000 RIBs have been made more than 870

RIBs have been used in experiments


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In-flight fragmentation CCF facility at MSU(up to 1kW beam power, 16O 238 U)

MoNA (2003)

SECAR (proposed)

JENSA (2014)ANASEN, FSU (2013)

SuN (2012),

CFFD (2014)

JANUS..

BECOLA (2011)

AT-TPC (2013)

Cycstopper off line

commissioning

(2013)20 meter

Gas Stopper

2012

K500

C clotron

Sweeper

Magnet (2004)

MomentumCompression Beam

Line (2012)

LEBIT (2011)

ReA3

Hall

(2013)

ReAccelerator Facility (2011)

-

Hall

the science program

A1900 FragmentK1200

Cyclotron

SEETF

(2003) SeGA

HiRA (2003)BCS

NERO 2003S800 (1996) Helium Jet (2014/15)

Triplex Plunger (2012)CAESAR (2009)

LENDA (2010)

GRETINA (2012/13, DOE national user facility)

DDASCAESAR (2009)

Proton Detector

(proposed)

RFFS (2007)


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Applications of Accelerators in Nuclear

Physics [2] Accelerators as driver to produce rare isotope beams: Cyclotrons

D. Leitner, July 2013, Slide 7U

35+

~ 15pA (525 eA), Injector 350 Mev/u U ~ 0.5 to 1pA

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Physics [2] FRIB: in-flight fragmentation: fast, stopped, reaccelerated beams

D. Leitner, July 2013, Slide 8200MeV/u for Uranium, 8.4pA, 400kW on beam power for all ions

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Physics [2]

Sto ed Low Ener

FRIB: in-flight fragmentation: fast, stopped, reaccelerated beams

Fast Beam

Beams

Re

Nuclear

Physics

Experimental

Stopper

Fragment

Separator

x

Area

Target

Production Linac (2020)

Largest heavy ion SC linac worldwide

341 SRF cavities


=0.041, 0.085,0.29,0.53

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AcceleratorsApplications of Accelerators in Nuclear Physics and

Particle Physics [3]Relativistic heavy ions and particle physics

GeV to TeV/ nucleon of protons or heavy ions (RHIC and LHC, colliders):, .

Fixed target: GeV electrons (JLAB), protons (Fermilab)RHIC

rings with 6 interaction points

Can circulate heavy ions or protons

Chain of accelerators:

3 injectors (High charge state injector

(EBIS source+linac), Tandem injector,

proton linac)

Alternating Gradient Synchrotron

RHIC 2.4 miles circumference

storage ring


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K-factor: corresponds to the maximum kinetic energy a proton canreach/transport for the accelerator's maximum magnetic rigidity, B

Magnetic rigidity:

2 v

?max,,8 80 energyUTmB

,

pvMB

K

TmTm

MeV

A

K

)8(238

80

)(

3.48 22

222222

22

1

A

QK

B

M

QevME

nuceA

222

2

2

222

2

)(9382

)(2

)(2

BMeV

MeV

MeV

ceB

cm

ceB

m

eK

oo

p

22 )(][

. BTm

Kp

22 )(][. B

ATme

A


0

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K-factor: corresponds to the maximum kinetic energy a proton canreach/transport for the accelerator's maximum magnetic rigidity, B

Magnetic rigidity:

2 v

?max,,8 80 energyUTmB

,

pvMB

K

TmTm

MeV

A

K

)8(238

80

)(

3.48 22

222222

22

1

A

QK

B

M

QevME

nuceA

222

2

2

222

2

)(9382

)(2

)(2

BMeV

MeV

MeV

ceB

cm

ceB

m

eK

oo

p

22 )(][

.B

TmKp

22 )(][

. BATm

eA


0

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Electrostatic focusing versus magnetic focusing

zzv

LtV

m

eQv ,

2EQeFelectric

x

z

eQEt

xm2

2

magnetic

Focusing strength for

magnetic elements

increases with velocity,z

xx

z

xeQV

mE

m

eQLE

mv

eQLtE

m

eQx

2222

1 2

2

22

beams magnets need to

be used (electrostatic

elements are only used up

Electrostatic focusing is Q/A independent,

used for injection lines (e.g. post accelerators,

to a few MeV total beamenergy)

2 charge state injection, e.g. FRIB front end)


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FRIB front end accelerates and transports two charge statessimultaneously to the SC heavy ion linac

Beam is very slow 12keV/u(required injection energy for theRFQ linac)

CSS2

CSS1

Combines magnetic elements andelectrostatic focusing elements toselect and trans ort two char e

(Injector 1)

states

Other uses for electrostatic

(Injector 2)

breeders in post accelerators ,electron microscopes, focusingelements electrostatic

Vertical

Beam lineMEBT

.RFQ


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A Brief Accelerator History

DC Acceleration

1927: Lord Rutherford requested a

Van de Graaff

(1929) MIT, c.1940s

5 MV

energetic than natural alpha and beta

particles. At the opening of the

resulting High Tension Laboratory,

u er or wen on o re era e e goa :

What we require is an apparatus to

give us a potential of the order of 10million volts which can be safel

accommodated in a reasonably sized

room and operated by a few kilowatts

of power. We require too an exhausted

voltage I see no reason why such a

requirement cannot be made practical.


1D. Leitner, July 2013 15

http://libraries.mit.edu/archives/exhibits/van-de-graaff/

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DC Acceleration: Pelletrons/Tandems

Pelletrons and Tandems (injector or stand alone)

HV Terminal

Charging belts

Pressure Tank (SF6)

g energy s a y

Limited voltage typically few MV (25MV max)

SF filled

pressure tank

5.8MV/m

vacuum nsu a orinterface

2MV/m



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Cockcroft and Walton

Voltage Multiplier

Series of diodes and ca acitors

converts AC power to DC power

through several stages

Used also switching power supplies

ra ona n ec or or g energyaccelerators

Today mainly replaced by RFQ

Radio Fre uenc Quadru ole



linacs)

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How can we get to higher energies?

DC accelerators are limited by a maximum size and a maximum breakdown voltage

length to the growing velocity of the particles and rf frequency, one canapply relatively low accelerating voltages at each acceleration step

Use one or a small number of

radiofrequency accelerating

Use many accelerating cavities

through which the particlecav es an ma e use o repea e

passage through them

passes on y once.


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How can we get to higher energies?

DC accelerators are limited by a maximum size and a maximum breakdown voltage

length to the growing velocity of the particles and rf frequency, one canapply relatively low accelerating voltages at each acceleration step

First principles were developed in the 1930s

Wiederoe 1929: First linear drift tube asdemonstration ex eriment50 keV; accelerated heavy ions (K+, Na+),utilized oscillating voltage of 25 kV @ 1 MHz

Lawrence 1930 read looked at Wiederoes

paper, was aiming to make the design morecompact by adding a magnetic bending field


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Cyclotron acceleration 5 inch diameterwax vacuum seal!

Acceleration while crossing the gap

Dummy Dee at ground

R

vMRBvQe

2

, 80keV protons

BQe

Rotation frequency

is independent of the

velocity

vM

Radius grows with

growing velocity

BQe Acceleration Dee, connected to

*

Energy gain dependsquadratic on Q

D. Leitner, July 2013, Slide 20A

QK

BR

M

QevME

222222

22

1

,

Cyclotrons can have many Dees

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Linear accelerators

Create a series of resonant cavities for one time path

Match drift spaces with growing velocity

,

v

f

c

c

v

)cos(),0(

22

0

tEtE

c

z

o ages sw c es

polarity as particles

travel through drift

tube (-mode)

o e r u esshould be /2

apart, bunches are

apart


Room temperature drift tube linac

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Radio Frequency Quadrupole Linac

Electrostatic Quadrupole

Transport channel

Acceleration is added

as perturbation

D. Leitner, July 2013, Slide 22/2

at MSU, energy gain 12keV/u to 600keV/u

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Linear accelerators

= , e par c e s n e cen er o e cav y, an as a p ase p re a ve o

the maximum field

Energy gain

depends linear on q

D. Leitner, July 2013, Slide 23Transit Time Factor TTF

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Linear accelerators

= , e par c e s n e cen er o e cav y, an as a p ase p re a ve o

the maximum field

TT

F

D. Leitner, July 2013, Slide 24Transit Time Factor TTF=v/c

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TTF for 2 or more gaps

= . .normalized velocity, for cavities with

different number of gap

d

SC linac have typically individually phased cavities

with a few gaps

2

,

The larger the number of gaps the larger the energy

gain, but longer cavity structures are needed

The individual accelerator arrangement will depend

For more than 2 equal

gaps in mode, the

25

upon the evolution of the particle velocity along the

system

formulas change only in

the 2ndorder term

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Different Arrangements for DifferentParticles

Accelerating system used will depend upon the evolution of theparticle velocity along the system electrons reach a constant velocity at relatively low energy

thus, can use one type of resonator

heavy particles reach a constant velocity only at very high energy thus, may need different types of resonators, optimized for different velocities


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FRIB driver linac accelerates heavy ionsQWR

s .

QWR

s .

TTF for the FRIB cavities

HWR


s .

HWRs=0.29

=v/c

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Normal vs. Superconducting Cavities


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Keeping FocusedWeak Focusing

Without focusing the particles do not experience any restoring force iny-direction, spiral out of control

The magnetic field decreases with radius and thus provide restoringforce

Be Classic cyclotron were build this way, but

M

Frequency changes!

R0d


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Path to higher energiesstrong focusing (alternate gradient focusing)

In the classic cyclotron focusing requires

but isochronicity requires in order to maintain

0R

B

0B BQe

Sector focusing cyclotron : B increases with R and has spiral magnet-,

RF Cavities

Magnet

Valleys

agnet

Hills

Position of the Sector Magnets


supercon uc ng sec or ocus ng cyc o ron en er eg on,

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RIKEN RI Beam Factory

RIKEN SRC, K2500, biggest SC cyclotron: 440 MeV/nucleon for lightions and 350 MeV/nucleon for heavy ions (Uranium)

800 tons/SC sector magnet

8300 tons total weight

Last acceleration station forthe RIBF RIKEN.


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Linear Restoring Forces [1]

Wish to look at motion near the ideal trajectory of the accelerator system

Assume linear guide fields

= = ,

')(

xBBxsdB

BB y

x

1

ds

svxdt

ds

ds

dx

dt

dx ' '

)( yBy

dy

sdBB

x

xx

X

xxdds

xdds

dds

)(1

0,' BBdxdy

s yxd

xXX

dds

Xd design trajectory

X...actual trajectory

32M. Syphers Aug 2012 32

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Linear Restoring Forces [2]

Wish to look at motion near the ideal trajectory of the accelerator system

Assume linear guide fields

= = ,

Look at radial motion:[1]

[2]

22 'xd

svxdt

ds

ds

dx

dt

dx '

2 s

dt

xvs 11

vs

pB


e

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Hills Equation

Now, for vertical motion:

By= B0+ Bx

So we have,

x= y

to lowest order,

e

pB 0

Hills E uation

General Form:


,

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Piecewise Method of Solution

n Hills Equation:

Thou h K s chan es alon the desi n tra ector , it is

typically constant, in a piecewise fashion, through

individual elements (drift, sector mag, quad, edge, ...)

K = 0:

K > 0:

K < 0:

Here,xrefers to horizontal or vertical motion, with

35M. Syphers Aug 2012

re evan va ue o

35

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Piecewise Method -- Matrix Formalism

Write solution to each piece in matrix form

for each, assume K= const. from s=0 to s=L

K= 0:

K> 0:

K< 0:


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Thin Lens Quadrupole

If the quadrupole magnet is short enough, particles offset through the quad does notchange by much, but the slope of the trajectory does -- acts like a thin lens ingeometrical optics

Take limit as L --> 0, while KL remains finite

(similarly, for defocusing quadrupole)

Valid approx., if F>> Lx(s)

sF

By

LxLBeB

LL

x y

''

Change of the transverse directory

Bp


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Piecewise Method -- Matrix Formalism

ininout x

x

LL

Lf

L

x

x

f

L

fx

x

'1

1

'11

01

10

1

11

01

'2

Arbitrary trajectory, relative to the design trajectory, can be computed viamatrix multiplication

sN

x

Matrix formalism (using beam envelope) is the basis of now-

standard computer codes for analysis: TRANSPORT, MAD,


, , ,

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Stability Criterion

For single pass through a short system of elements, above may be all we need

to know to describe the system. But, suppose the system is very long and

made of many repetitions of the same type of elements (or, perhaps the

repetition is a complete circular accelerator, for instance) -- how to show that

the motion is stable for many (infinite?) passages?

Look at matrix describin motion for one assa e:

We want:


Stability Criterion

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Stability Criterion

V = eigenvector

= eigenvalue

If is imaginary, then repeated application of Mgives,


Example: Application to FODO system

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Example: Application to FODO system


Motion is stable provided that the lens spacing is less than twice the focal length

Can now make LARGE accelerators!

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Can now make LARGE accelerators!

Since the lens spacing can be made arbitrarily short, withcorresponding focusing field strengths, then in principal can makebeam transport systems (and linacs and synchrotrons, for instance)of arbitrary size

Instrumental in paving the way for very large accelerators, both

linacs and especially synchrotrons, where the bending and focusingfunctions can be separated into distinct magnet types


What about longitudinal stability?

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What about longitudinal stability?

s0 s0

is the energy gain in one gap for the particle to reach, ,

are fixed points in phase. P1 and P2 would allow for

the same acceleration, but operation point P2 would

be unstable

N1 arrives early at the cavity (get less acceleration), M1 will arrive late at thecavity (get more acceleration, P1 is the synchronous particle. So M1 and N1

will move towards P1(stable).


(M2& N2will go away from P2(unstable))

Longitudinal beam dynamics

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Longitudinal beam dynamics

If the ideal particle has energy Es and arrives at phase s ...

particles arriving nearby in phase, and nearby in energy E = Es +E will oscillate

about this ideal condition, particles are transported in bunches

Buckets

Stable Phase Space regions Separatrix


Acknowledgements and additional info

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Acknowledgements and additional info

an s o e yp ers, ra err , an e eam orsharing class slides!

Slides were also used from the MSU course Accelerator Physics ofFRIB -- PHY905, 2011

Want to learn more?US Particle Accelerator School! Held twice earl at venues across thecountry; offers graduate credit at major universities for courses inaccelerator physics and technology (lecture notes!)

Interested in joining the FRIB team?

. .

Interested in becoming involved inthe evolving user community?


.

Appendix

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Appendix


Finally a quick tour an accelerator under

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Finally a quick tour an accelerator underconstruction

HighpowerCW

superconductingdriverlinac

400kWbeam ower

AdvancedECRionsources+

multiplechargestateacceleration 5chargestatesintheLINAC

cce era es eams romp

MeV/u)toU(200MeV/u)

HighPowerTarget

,

directfromthefragment

separator

Efficientpostaccelerationfrom

1+andn+ionsources

3MeV uAstro h sics


12MeV/uNuclearPhysics

FRIB front end produces and pre-l t th i b

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accelerates the primary beam


Double folded heavy ion driver linac

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y

5 charge states on target (1-2 mm spot)

Lithium Charge Stripper

5 charge state selected (4 cm dispersion)

LINAC Segment 1 : 17MeV/uLINAC Segment 2 : 148MeV/u

LINAC Segment 3: 201 MeV/u


Paperclip design to reduce construction

costs but complicates beam dynamics

P d ti t t d f t t

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Production target and fragment separator

Prompt radiation at 30 cm

distance from target (neutrons,

rotons : 100 Mrem/h 108 rem/h

Total weight of steel shielding in

target hot cell: 3900 tons

3 separation stages provide high

purity.400 kW beam power 238U is 5x1013 ions/s.

rare isotopes with beam rates of less than10-3/s. This means a suppression of

unwanted ions by factors of 1017 or higher

.

Production target

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Production target

Power density in target ~ 20 - 60 MW/cm3

Caused by 1 mm beam spot on target and high energy loss of heavy ions in matter (upto 100 kW deposited in target)

Target lifetime at full power expected to be 2 weeks Target needs to be replaced with remote-handling equipment

Prompt radiation at 30

cm distance from target

(neutrons, protons): 100Mrem/h (108 rem/h)

Re-Accelerator facility is a state-of-the-art RIB post-l t d th fi t l d t f t ti f ilit

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accelerator and the first coupled to a fragmentation facility

EBIT CB

RFQ

CM2CM1

SECAR

CM3 (2014)

First experimental beam line

will be commissioned thissummer

ReA3 AT-TPC-

N4 Stopped beams

A1900

L-Line

ReA6ReA6 Equipment

& Beamlines

TBDRe-Accelerator Concept

Cryomodule5,6=8.5%

Cryomodule4=8.5%

Cryomodule3=8.5%

Cryomodule2=4.1%

CM14.1%

RFQ

M

HB

1+n+

A1900>50MeV/u

ExperimentsMassseparation

Gas

Stopper

Leitner, State-of the-art RIB post accelerators, NIMB, accepted (2013)

ReAccelerator is a state-of-the-art compact

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SC linac wide energy range

Q/A Cryomodule 5,6=8.5%

Cryomodule 4

=8.5%

Cryomodule 3

=8.5%

Cryomodule 2

=4.1%

CM 1

4.1%RFQ

M

H

B

ReA3 (15 cavities)

(2014)

ReA6

(+10 cav.)

(2016)

ReA12

(+16 cav.)

proposed

1+n+

Mass

separation

CCF FRIB

A1900

>50MeV/u

Experiments

(starting2013)Gas

Stopper

equ remen s

Energy variability while

preserving beam properties

300keV/u

12MeV/u

Independently phased and tuned SC

RF cavities and rebunchers

on e c ency or a

elements

> c arge ree er + g

efficiency LINAC

Beam rate capabilities 108 ions/sec Hybrid EBIS/T charge breeder


High beam purity A1900, EBIT CB, Q/A

Low energy spread,

short pulse length

1keV/u, 1nsec Multiharmonic external buncher and

tight phase control in SRF linac

2020

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2020

Documents

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