Particle Sources Dan Faircloth

Rutherford Appleton Laboratory

-The most important part of the whole

machine

CAS Prague 2014

Light ions

e.g. С4+

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

Highly charged ions e.g. Ag32+

Exotic nuclei e.g. Lr103+

Polarised particles

Neutrinos νe νμ ντ

Photons

Higgs Bosons

Zoo of curiosities

Mesons Tauons

Fully stripped nuclei e.g. U92+

W + Z Bosons

Baryons

p

e–

H–

Positively Charged Particles Negatively Charged Particles

Neutral Particles

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons

Surface converter

Surface plasma

Volume

Multicusp Filament

and

RF

Plasmatrons

Microwave discharge

Electron Cyclotron

Resonance

Electron beam

Laser plasma

W + Z Bosons

Baryons

Thermo

Photo

Plasma + other

Penning and

Magnetron

p

e–

H–

Vacuum arc

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

The Electron!

George Johnstone Stoney J. J. Thomson 1897 1894

Corpuscles Electrons

Hermann Sprengel

Improved mercury pump 10-5 mBar

Early 1870’s

William Crookes

Electron Guns

Inferiority complex…

Ion Sources ?

Particle sources/guns consist of:

An extraction system to create and accelerate a

beam

+ Something to make the particles

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Thermionic

Fredrick Guthrie British scientific writer and professor

Elements of Heat in 1868

First experimental observation of thermionic emission

A negatively charged red hot metal ball

looses charge...

- + ...whereas a positively charged one keeps its

charge

Thermionic Emission

1880 Thomas Edison The “Edison effect”

+ -

+

-

Ammeter

0

-

+

Swap polarity

Thermionic Emission

1880 Thomas Edison The “Edison effect”

+ -

+

-

Ammeter

0

-

+

Thermionic Emission

1901 Owen Richardson

kT

W

G eTAJ

2

J. J. Thomson 1897

Corpuscles

Same form as the Arrhenius equation

Cambridge University

Richardson’s Law

Current increases exponentially with temperature

Thermionic Emission

kT

W

G eTAJ

2Lowest possible work function Highest possible temperature

Nu

mb

er

of

Elec

tro

ns

Energy Ef

Fermi Level

E0

Vacuum Level

W

Work Function

Free electrons

Fermi-Dirac Statistics @ 0 °K

= a few eV

For a good electron emitter you need:

Cathode Materials W

ork

Fu

nct

ion

(eV

)

Practical Operating Temperature (Kelvin)

BaO W ≈ 1 eV

5

1

2

3

4

0 3000 2000 1000

CeB6

LaB6

W ≈ 2.5 eV

High brightness

Commonly used

Ideal material (does not exist!)

Cs 1.9 eV

Ta 4.1 eV

W 4.5 eV Mo

4.2 eV

Child-Langmuir Law (Space charge limited extraction)

Cathode Anode

Elec

tro

n

bea

m

Ground EEmission

d

Q

VCathode

2

2

3

0

2

9

4

d

Vm

e

je

C.D Child

1911 Irving Langmuir

1913

Electron emitting material

Perveance

IBeam

VExtraction

P

VExtraction

Perv

ean

ce L

imit

I

Elec

tro

n

bea

m

Cathode Anode

Ground VCathode

Pierce Extraction Geometry

Pierce Extraction Geometry

Elec

tro

n

bea

m

Ex = Ey = 0

Cathode Anode

67.5°

Ex = Ey = 0

Ground VCathode

Gridded Extraction

Elec

tro

n

bea

m

Cathode Anode

Heater

(A triode amplifier)

Ground

Vgrid

VCathode

1cm2

12 W heater

Swiss Light Source

90 kV triode gun with Pierce geometry

YU 171

Sinter of W and BaO

1000 ns, 3 nC long pulses or

1 ns, 1.5 nC short pulses

Thermionic dispenser cathode with integrated heater and grid

Lifetime = several thousand hours

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Thermionic

Photo

Photo Emission

First observed by Heinrich Hertz in 1887

Theoretical explanation by Einstein in 1905

UV

Photo electric emission

Nu

mb

er

of

Elec

tro

ns

Energy Ef E0

Fermi Level Vacuum Level

W

Work Function

Free electrons

Quantum efficiency (QE) =

Photons (of high enough frequency)

Number of electrons produced Number of incident photons

Photo Emission Gun

Cathode Anode

Ground

Laser beam Materials: Cu QE 0.001% GaA QE 5% Cs2Te QE 10%

Photo cathode

Elec

tro

n

bea

m

VCathode

Cornell DC Photoemission gun

20 mA average current at 250kV

Space Charge

Space Charge

Space charge force scales as 1/γ2 At 500 keV

electron γ= 2

(940 MeV proton γ = 2)

Lasers are so fast they can easily beat Child-Langmuir (to be fair, so can

gridded extraction)

Another reason to use lasers is…

“Pancake” beam

Very short laser pulse

C.D Child

1911 Irving Langmuir

1913

Cathode Anode

Ground

Cs2Te

Photo Cathode

Emitted current is not

limited by space charge

Very short Beam pulse

Cathode Anode

Ground

Cs2Te

Photo Cathode

EEmission

VCathode

RF Photemission Source

“Pancake” beam pulses

Photo Cathode

Very short laser pulses

Cs2Te

RF Photemission Source

Resonant RF cavity (normal or super conducting)

Laser pulse High Fields

> 10 MVm-1

RF feed

RF feed 1.3 GHz

1.3 GHz

EEmission

Time

RF waveform

EEmission

Laser pulse

20 ps, 1 nC pulses (50 A pulse)

15 ps, 1 nC pulses (67 A pulse)

High brightness low emittance guns for FEL

Normally conducting Super conducting

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Thermo

Photo

Plasma + other

Other electron sources:

Plasma chamber

Plasma Cathode

Very high electron currents can be extracted from plasma cathode electron sources

Cathode Anode

Ground

> 1kA! Rarely used in accelerators: Field emission from needle arrays Diamond amplifiers Etc...

Combinations of those already mentioned e.g. photo-thermionic

Long cathode lifetimes

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Plasma Sources

Particle Sources

Ionisation e-

Neutral Atom

Most sources rely on electron impact ionisation

Ionisation e-

Neutral Atom

Most sources rely on electron impact ionisation

Ionisation

Most sources rely on electron impact ionisation

e- e-

Positive Ion

Electrical Discharges

Arc Discharge

Glow Discharge

Log I

Breakdown Voltage

µA

nA

A

100 A A

pp

roxi

mat

e C

urr

ent

Ran

ge

Thermal Arc Discharge

70 V

Dark Discharge Townsend Breakdown

Voltage Between Anode and Cathode

Background Ionisation

Arc Discharge

Glow Discharge

Breakdown Voltage

µA

nA

A

100 A A

pp

roxi

mat

e C

urr

ent

Ran

ge

Thermal Arc Discharge

70 V

Dark Discharge Townsend Breakdown

Voltage Between Anode and Cathode

Background Ionisation

Quark Gluon Plasma

Fusion

Z-Pinch 1M A

1G A

Basic Plasma Properties

Density, n (per cm3) ne = density of electrons

ni = density of ions

nn = density of neutrals

Charge State, q H+ → q = +1

Pb 3+ → q = +3

H– → q = -1

Temperature, T (eV) Te = temperature of electrons

Ti = temperature of ions

Tn = temperature of neutrals

11600°K = 1 eV

Temperature Distribution

If thermalised velocity

distributions should follow

Maxwell Boltzmann statistics

However, in magnetic fields:

vx ≠ vy ≠ vz

Magnetic Confinement

Particles spiral along magnetic field lines

Dipole field

B

Solenoid field

Hexapole

N

S

S S

N

N

Multicusp Confinement

Collisions

Relaxation time = 90° deflection time e-

e-

Concept of mean free path does not work in a plasma

Charged particle trajectories are constantly affected by their neighbours electric fields > 90°

The average time it takes for a particle to be deflected by 90 °

Percentage Ionisation

ni + nn

ni

> 10 % → Highly ionised < 1 % → Weakly ionised

Quasi Neutrality

Σ qi ni = ne

Debye Length

e-

e-

Plasma Sheath

Electrons have a greater mobility

Cathode Anode

Sheath Quasi neutral plasma

at anode potential

Vanode

Vo

ltag

e

Distance Vcathode

Vanode

Vcathode

Heinrich Geißler Julius Plücker

Gas discharge tube and mercury displacement pump just less than 1 mBar

Mid 1850’s University of Bonn

magnetism could move the glow discharge

Plasma Pioneers

Drawing of Geissler tubes from 1860’s French physics book

Canal Ray Source

In 1886 Eugen Goldstein discovered canal rays

Perforated Cathode

Anode Glass Tube

Vacuum Pump

Discharge Power Supply

1-100 V

Positive Ion

Beams

+ - Discharge Power

Supply 0.1 -10 A

Electron Bombardment Source (1916)

Filament Power Supply 2-10 A

Beam

Extraction Voltage Supply 1-10 kV

- +

Arthur Dempster

Extraction Electrode

Gas Feed

Anode

Cathode Filament

Early mass spectrometry

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Plasmatrons

Plasmatron (late 1940s)

Beam

Manfred von Ardenne

Filament Power Supply 2-100 A

Gas Feed

Extraction Voltage Supply 5-50 kV

Discharge Power Supply 2-100 A

Extraction Electrode

Cathode Filament

Anode

+ -

- +

Conical Intermediate Electrode

Duoplasmatron (1956)

Beam

Manfred von Ardenne

Anode

Filament Power Supply 2-100 A

Gas Feed

Cathode Filament

Discharge Power Supply 2-100 A

+ -

+ Extraction Voltage

Supply 5-50 kV

Extraction Electrode

-

Solenoid Field Iron Return Yoke

Conical Iron Funnel Intermediate

Electrode

Expansion Cup

Defocusing Solenoid

Solenoid

CERN Duoplasmatron

300 mA protons 150 μs pulses at 1 Hz

Particle sources/guns consist of:

Something to make the particles

An extraction system to create and accelerate a

beam

+

The emission surface is critical to the quality of the beam

Plasma Mencius

Bea

m

Bea

m

Pla

sma

Plasma Electrode

Extraction Electrode

Men

iscu

s

Convex

Pla

sma

Plasma Electrode

Extraction Electrode

Men

iscu

s

Flat

Plasma Electrode

Extraction Electrode

Men

iscu

s

Concave

Pla

sma

Bea

m

Not including space charge effects

Space Charge Plasma

Electrode

Extraction Electrode

Men

iscu

s P

lasm

a

Percentage compensation

Neutralising Particles

≈ 95% 0%

Bea

m Optimum =

slightly concave

Suppressor Electrode

Plasma

Plasma Electrode Suppression Electrode

Ground Electrode

Extracted Beam

Compensating particles reflected by the Suppression

Electrode

V (kV)

Z (mm)

Emittance of Real Beams

Halo Effect - Plasma boundary - Fringe fields

95% emittance

rms emittance

How big is this beam?

Brightness

Be careful- Some definitions include factors of 2, 8 and π Are the emittances normalised?

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Microwave

Microwave Ion Sources

Off resonance = Microwave discharge ion sources

On resonance = Electron Cyclotron Resonance (ECR) sources

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Microwave discharge

Plasmatrons

Microwave Discharge Ion Source

Beam

Solenoids

Stepped RF Matching Section

RF in

≈ 100 mm

Plasma Chamber

High Voltage Insulators

Plasma Electrode

Ground Electrode

Suppressor Electrode

Discharge Region

Gas Feed

2.45 GHz commonly used

SILHI Microwave Source

Rafael Gobin CEA Saclay Late 1990s

140 mA DC protons For one year!

Sophisticated Extraction System

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Plasmatrons

Microwave discharge

Vacuum arc

Vacuum Arc Ion Sources

≈ 50 mm

Beam

Anode Trigger

Electrode

Cathode

Solenoid Ground Electrode

High Voltage Insulators

Suppressor Electrode

Extraction Aperture

Grids

Expansion Region

1980s - Ian Brown and others

Lawrence Berkley Lab MEVVA

15 mA of U4+ ions

GSI MEVVA

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Plasmatrons

Microwave discharge

Laser plasma Vacuum

arc

Target Chamber

Laser Plasma Ion Sources

≈ 200 mm

Beam

Plasma Plume

High Power Laser

Laser Beam

Expansion Region Extraction

Aperture

Focusing Optics

Target

Target Rotation

Mechanism

High Voltage Insulators

Ground Electrode

Suppressor Electrode

Salt Window

1 -100 Joules per pulse!

ITEP Laser source at CERN

Target Vessel

Final Optics

ITEP Laser source at CERN

TWAC at ITEP Moscow

7 mА, 10 μs pulses of С4+

Masahiro Okamura has demonstrated Direct Plasma Injection into an RFQ

BNL and RIKEN

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

Dan Faircloth CAS 2012

p

e–

H–

Plasmatrons

Microwave discharge

Laser plasma Vacuum

arc

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

Dan Faircloth CAS 2012

p

e–

H–

Electron Cyclotron

Resonance

Microwave Discharge Ion Source Solenoids

Stepped RF Matching Section

RF in

≈ 100 mm

Plasma Chamber

High Voltage Insulators

Plasma Electrode

Ground Electrode

Suppressor Electrode

Gas Feed

ECR Ion Source

Beam

Super Conducting Solenoids

Stepped RF Matching Section

RF in

≈ 100 mm

Plasma Chamber

High Voltage Insulators

Plasma Electrode

Ground Electrode

Suppressor Electrode

ECR Surface

Hexapole Magnetic Field

Gas Feed

A

B

B

Section on B-B Section on A-A

A

ECR Surface

Beam RF in

ECR Surface

28 GHz superconducting VENUS ECR

200 eμA U34+ ions 4.9 eμA U47+ ions

Daniela Leitner LBNL Late 2000s

VENUS ECR

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Electron Cyclotron

Resonance

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Electron beam

Electron Beam Ion Sources

Z

Drift TubeV

Trapping and Ionisation Phase

Superconducting Solenoid Magnetic Shielding

Electron Dump

≈ 100 mm Ionisation Chamber

Drift Tubes Electron Beam Electron Gun

Extraction Electrode

Stepwise ionisation

Electron Beam Ion Sources

High Charge State Positive Ion Beam

Drift TubeV

Z

Extraction Phase

Extraction Electrode

Superconducting Solenoid Magnetic Shielding

Electron Dump

≈ 100 mm Ionisation Chamber

Drift Tubes Electron Beam Electron Gun

1.7 emA, 10 µs, 5 Hz Ag32+ ions

Jim Alessi BNL

Fully stripped nuclei can be obtained in EBIT mode

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Negative Ion Sources

Ripping electrons off is easy!

- It is much harder to add them on….

Not all elements will even make negative ions

Hydrogen has an electron affinity of 0.7542 eV

H– has a much larger cross section than H0

30 times for e- collisions

100 times for H+ collisions

H– are very fragile!

Tandem accelerators Cyclotron extraction

Protons

H- from Linac

Stripping

foil

Multi-turn injection into rings

Neutral Beams

Applications

Early attempts at producing negative ion beams:

1. Charge exchange of positive beams in gas cells

- very inefficient

2. Extraction from existing ion sources

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Surface plasma

Early 1970s Budker Institute of Nuclear Physics Novosibirsk

Production of H– ions by surface ionisation with the addition of ceasium

Gennady Dimov

Surface Plasma Sources (SPS)

Vadim Dudnikov Yuri Belchenko

Caesium!

1 electron in the outer

orbital

More reactive

– The magic elixir

An amazing donor of electrons = great for making negative ions

5 g Caesium Ampoule

Caesium coverage and work function

4.6

Cs Thickness (monolayers)

2.1

1.5

0.6 1

Wo

rk F

un

ctio

n (

eV)

Pure molybdenum

Pure Caesium

Fermilevels

Cs

Cs

Cs

P

H

H

Caesium oven

temperature

1.0E-04

1.0E-03

1.0E-02

1.0E-01

100 120 140 160 180 200

Cs Oven Temperature (Degrees C)

0.00

0.01

0.02

0.03

0.04

0.05

100 120 140 160 180 200

Cs Oven Temperature (Degrees C)

Pre

ssu

re (

mB

ar)

Pre

ssu

re (

mB

ar)

Log Scale

Caesium vapor

pressure

Control caesium coverage

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Surface plasma

Penning and

Magnetron

Anode Anode Cathode

Magnetron SPS

≈ 10 mm

Hydrogen Hydrogen

Caesium Vapour

Beam

B

Extraction Electrode

Cathode

Extraction Electrode

H– Beam

Electrons

Magnetic Pole Pieces

B

80 mA of H– but only at low duty cycles < 0.5%

BNL Magnetron

Penning SPS

• Invented by Dudnikov in the 1970’s

• Very high current density > 1 Acm-2

• Low noise

• Does not work without ceasium

Mounting Flange

Negative Ion Beam

Mica

Penning Pole Pieces

10mm

Aperture Plate

Water Cooling Channels

Source Body Air Cooling Channels

Ceramic Spacer

Copper Spacer

Cathode

Hollow Anode

Discharge Region

Extraction Electrode ISIS Penning

H2

Negative Ion Beam

Piezo Hydrogen Valve

Caesium Oven

Caesium Vapour Heated Transport

Line

Hollow Anode

50 A Discharge

+17 kV Extraction Voltage

10mm

H2

Negative Ion Beam

Piezo Hydrogen Valve

Caesium Oven

Caesium Vapour Heated Transport

Line

Hollow Anode

50 A Discharge

+17 kV Extraction Voltage

10mm

Source Runs at 50 Hz

Rep Rate

Cathode

Hydrogen Feed

Heated Caesium Transport Line

Air Cooling

Source Body

Hollow Anode

Discharge Power Feed

Thermocouples

Aperture Plate

Extraction Electrode

Support Insulators

Caesium Shields

Extraction Mount

60 mA 1 ms 50 Hz H– beams

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Surface converter Multicusp

Filament

Surface plasma

Filament Cathode Multicusp Surface Converter Source

Anode

Anode

Multicusp Magnets Multicusp

Magnets ≈ 100 mm

H– Beam

Outlet Aperture

Caesium Vapour

Hydrogen Feed

Heated Filament Cathode

Surface Converter Electrode

-300 V

LANL: 18 mA 1 ms 120 Hz H– beam

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Volume

Volume Production

Marthe Bacal Ecole Polytechnique

mid 1970’s

H2* + e (≤1 eV) → H– + H0 Dissociative attachment of low energy electrons

to rovibrationally excited H2 molecules

Developed by Ehlers + Leung at LBNL

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Volume

Multicusp Filament

Multicusp Filament Volume Source

Many Variations: e.g. JPARC use a LaB6 cathode

≈ 100 mm

Hydrogen feed

B

Electron dump

H– Beam

Extraction electrode

Cathode

Filament

Anode

Low electron temperature plasma

region Multicusp magnets

Section on A-A

Multicusp magnets

Plasma chamber

A

B

B

Section on B-B

A

High electron temperature

plasma region

Filter magnets

Plasma chamber

D-Pace 15 mA DC H– Multicusp Volume Source

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Volume

Multicusp RF

≈ 100 mm

Plasma chamber

B

Electron dump

H– beam

Extraction electrode

Cathode

filament

Anode

Low electron temperature plasma

region

Section on A-A

Multicusp magnets

Plasma chamber

A

B

B

Section on B-B

A

High electron temperature

plasma region

Filter magnets

Internal RF Solenoid Antenna Volume Source

≈ 100 mm

Plasma chamber

B

Electron dump

H– beam

Extraction electrode

Anode

Low electron temperature plasma

region

Section on A-A

Multicusp magnets

Plasma chamber

A

B

B

Section on B-B

A

High electron temperature

plasma region

Filter magnets

RF Power Supply

50 kW

External RF Antenna Multicusp Source

≈ 100 mm A

B

A

B

B

Section on B-B Section on A-A

Multicusp magnets External antenna solenoid

Funnel and aperture electrode

Electron dump

H– Beam

Multicusp magnets

Ceramic plasma chamber

Pulsed hydrogen

Ignition element

External Antenna solenoid

Ceramic plasma chamber

Extraction electrode

Filter magnets

Ignition anode

DESY Source

Jens Peters Late 1990’s

40 mA H–

150 μs, 3 Hz

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons W + Z

Bosons Baryons

p

e–

H–

Volume

Multicusp RF

Best of both worlds?

SNS ion source

38 mA H– 1 ms, 60 Hz

CERN are developing a ceasiated external antenna source for LINAC4

Light ions

e.g. С4+

Fully stripped nuclei

Particles and Sources

Higgs Bosons

Highly charged ions

Neutrinos

Exotic nuclei

Negative ions

H–

Protons Antiprotons

Neutral particles

H0

Electrons

e–

Neutrons n

Positrons e+

Muons μ– μ+

e.g. Ag32+

e.g. U92+

e.g. Lr103+

Polarised particles

νe νμ ντ

Photons

Zoo of curiosities

Mesons Tauons

Surface converter

Surface plasma

Volume

Multicusp Filament

and

RF

Plasmatrons

Microwave discharge

Electron Cyclotron

Resonance

Electron beam

Laser plasma

W + Z Bosons

Accelerator Facilities

Baryons

Thermo

Photo

Plasma + other

Penning and

Magnetron

p

e–

H–

Vacuum arc

Which Source?

• Type of particle

• Current, duty cycle, emittance

• Lifetime

• Expertise available

• Money available

• Space available

Reliability

• Operational sources should deliver >98% availability

• Lifetime compatible with operating schedule

• Ideally quick and easy to change

• Short start-up/set-up time

– is King!

Reliability also depends on:

Everything Else!

high voltage power supplies

vacuum systems

control systems

human error

mains power

temperature controllers

compressed air supplies

cooling water

hydrogen

material purity

low voltage power supplies

laser systems

machine interlocks

personnel interlocks

timing systems

cryogenic systems

communication systems

Developing Sources

Driven by demand for

– Increases in current, duty cycle and lifetime

– Improvements in beam quality

Development strategy

• Simulations

• Test stands

• Diagnostics

The Development Cycle

Hardware

Experiments Simulations

Summary

• Particle sources are a huge interesting subject

• A perfect mixture of engineering and physics

• We have only scratched the surface

Thank you for listening