Chapter 3. Basic Instrumentation for Nuclear Technology

1
Chapter 3. Basic Instrumentation for Nuclear
Technology

• Outline of experiment
• ?? get particles (e.g. protons, )
• ?? accelerate them
• ?? throw them against each other
• ?? observe and record what happens
• ?? analyse and interpret the data

• Accelerators
• Detectors
• Reactors

2
1.Accelerators

• History-Why
• Particle Sources
• Acceleration stage
• Space charge
• Diagnostics
• Application

3
Natures Particle Accelerators
Examples from the nature electrostatic
discharge, a- and ß-decays, cosmic rays.

• Naturally occurring radioactive sources
• Up to 5 MeV Alphas (helium nuclei)
• Up to 3 MeV Beta particles (electrons)
• Natural sources are difficult and limited
• Chemical processing purity, messy, and expensive
  
• Low intensity
• Poor geometry
• Uncontrolled energies, usually very broad

4
Start the ball rolling

• 1927 Lord Rutherford requested a copious
  supply of projectiles more energetic than
  natural alpha and beta particles. At the opening
  of the resulting High Tension Laboratory,
  Rutherford went on to reiterate the goal
• What we require is an apparatus to give us a
  potential
• of the order of 10 million volts which can be
  safely accommodated in a reasonably sized room
  and operated by a few kilowatts of power. We
  require too an exhausted tube capable of
  withstanding this voltage I see no reason why
  such a requirement cannot be made practical.

5
Why study...

• The construction, design and operation of
  particle accelerators uses knowledge from
  different branches of physics electromagnetism,
  high frequency electronics, solid states physics,
  optics, vacuum technology, cryogenics, ...
• Learning about particle accelerator is a good
  opportunity to learn about many different
  physical phenomenon.

6
Why

• They have wide ranging applications well beyond
  physics health, life science, materials and even
  archaeology!

7
Early accelerators

• 1870 Discovery of the cathode rays by William
  Crookes- Charged rays - Propagation from the
  Cathode to the anode

A Crookes tube in which the Cathode rays are
deflected by a magnetic field.
Images source Wikipedia
1896 J.J. Thomson shows that the cathode rays
are made of particles and measure the
charge/mass ratio.These particles are called
electrons
8
Bremsstrahlung

• A charged particle emits radiation when it is
  accelerated.
• An electron that Coulomb scatters on a heavy
  nucleus will change direction gt acceleration
• Bremsstrahlung, braking radiation, is the name of
  the radiation emitted when a charged particle
  scatters on a heavy nucleus.

• When a charged beam hits an object, X-rays are
  emitted. This is used to produce X-rays in
  hospitals but it is also a source of hazardous
  radiations in accelerators.
• Bremsstrahlung is similar to synchrotron
  radiation that will be discussed later today.

Image source http//www.ndt-ed.org/EducationReso
urces/
9
Improved resolution

• In quantum mechanics the wavelength of an object
  is related to its energy by

• The reach better resolutions, the energy of the
  probe must be increased.
• The energy of the electrons in Cathodic ray tubes
  is limited by the electrostatic generators
  available.
• In the 1930s several generators where invented to
  produce high electric fields.

10
vacuum
Ion source
analyzer
acceleration
steering
11
1.Accelerators

• History-Why
• Particle Sources
• Acceleration stage
• Space charge
• Diagnostics
• Application

12
Particle sources

• How particles are first produced?
• How to extract particles with the right
  properties?
• What are the limitations of the sources?
• The quality of the source is very important. If
  the particles emitted by the source do not have
  the right properties, it will be very difficult
  and/or expensive to rectify it later.

13
Beams of nanoamperes to hundreds of amperes Very
thin to very broad beams (µm2 to m2) Negative
to highly charged state e to protein molecule
14
Emission of electronThermionic effect

• When a metal is heated more electrons can
  populate high energy levels.
• Above a certain threshold they electrons can
  break their bound and be emitted This is
  thermionic emission.

• (image source wikipedia)?

15
Emission of electronField effect

• Under a very intense electric field some
  electrons will be able to tunnel across the
  potential barrier and become free.
• This is known as field effect emission.

(image source answers.com)?
16
Emission of electronPhoto-electric effect

• A photon incident on a piece of metal can
  transfer its energy to an electron
• If the photon transfers enough energy the
  electron can be emitted.
• By using powerful lasers the photoelectric effect
  can be used to produce electron beams.
• This is known as the photo-electric emission.

(image source wikipedia)?
17
Fermi-Dirac statistics
18
Work function

• To escape from the metal the electrons must reach
  an energy greater than the edge of the potential
  well.
• The energy that must be gained above the Fermi
  energy is called the work function of the
  metal.
• The work function is a propertyspecific to a
  given metal. It canbe affected by many
  parameters(eg doping, crystaline state,surface
  roughness,...)?
• Example values

(image source wikipedia)?
19
Summary electrons in solids
(image source http//cnx.org/content/m13458/lates
t/

• At low temperature all electrons are in the
  lowest possible energy level, below the Fermi
  level.
• As the temperature increase some electrons will
  go above the Fermi level.
• But only those with an energy above the Fermi
  level greater than the work function are free.

20
Thermionic emission

• The Richardson-Dushman equation gives the
  electronic current density J (A/m-2) emitted by a
  material as a function of the temperatureWith
  A the Richardson constant

(image sourceMasao Kuriki, ILC school)?
21
Thermionic cathode material

• Two parameters are important when considering a
  thermionic cathode material
• WWork function (as low as possible)?
• TeOperation Temperature (preferably high)?
• Cesium has a low work function (W2eV) but a low
  operation temperature (Te320K) gt not good for
  high current
• Metals Ta (4.1eV, 2680K), W(4.5eV, 2860K)?
• BaO has good properties (1eV 1000K) but can
  oxidize by exposure to air gt sinter of BaOWBaO
  provided slowly to the surface.

22
Electric field bias

• Once the electrons are free they may fall back on
  the cathode.
• To avoid this an electric field needs to be
  applied.
• If a negative potential is applied to the cathode
  the electrons will be attracted away from the
  cathode after being emitted.
• However this field affects the work function.

23
(No Transcript)
24
Photo-electric emission

• A photon incident on a material will transfer its
  energy to an electron present in the metal.
• If the energy of this electron becomes bigger
  than the work function of the material, the
  electron can be emitted.
• This is called photo-electric emission.

(image sourceMasao Kuriki, ILC school)?
25
Photo-electric emission (2)?

• A UV photon at 200nm carries an energy of about 6
  eV, this is enough to jump over the work
  function of most metals.
• As seen in electromagnetism, electromagnetic
  waves (photons) can penetrate inside a metal.
• The photo-electricemission may thustake place
  away from the surface.

(image source Dowell et al., Photoinjectors
lectures)?
26
The 3 steps of photo-electric emission

• Photo-electric emission takes place in 3 steps
• 1) Absorption of a photon by an electron inside
  the metal. The energy transferred is proportional
  to the photon energy.
• 2) Transport of the photo to the physical surface
  of the metal. The electron may loose energy by
  scattering during this process.
• 3) Electron emission (ifthe remaining energy
  isabove the work functionincluding Schottky
  effect)?

27
Quantum efficiency (QE)?

• For photo-electric emission, it is useful to
  define the quantum efficiency
• Typical QE for a photo-cathode is only a few
  percent or less!
• The quantum efficiency will decrease during the
  life of the cathode it may get damaged or
  contaminated.

28
Examples

• Which of these materials would give the highest
  thermionic emission current (at the same
  temperature)?
• Iron (Fe) W4.7 eV
• Gadolinium (Gd) W2.90 eV
• Cobalt (Co) W5 eV
• Which laser would give the best Quantum
  efficiency on a Copper-based photo-cathode (W5
  eV)?
• A 5GW CO2 laser (wavelength10 micrometers)?
• A 10 kW frequency doubled NdYAG laser
  (wavelength532nm)?
• A 3MW frequency quadrupled Ti-Sapphire laser
  (wavelength200nm)?

29
Ion source SINCS
Source of Negative Ions by Cesium Sputtering -
SNICS II
Principle of Operation
30
Focused Ion Beam
liquid metal ion source (LMIS),
31
Electrospray ionisation
Charge Residue Model electrospray droplets
undergo evaporation and fission cycles,
eventually leading progeny droplets that contain
on average one analyte ion or less. The gas-phase
ions form after the remaining solvent molecules
evaporate, leaving the analyte with the charges
that the droplet carried.
32
1.Accelerators

• History-Why
• Particle Sources
• Acceleration stage
• Space charge
• Diagnostics
• Application

33
Acceleration stage
Lorentz Force

• Only works on charged particles
• Electric Fields for Acceleration
• Magnetic Fields for Steering
• Magnetic fields act perpendicular to the
  direction of motion.
• For a relativistic particle, the force from a 1
  Tessla magnetic field corresponds to an Electric
  field of 300 MV/m

34
types of accelerators ?? electrostatic (DC)
accelerators ?? Cockcroft-Walton accelerator
(protons up to 2 MeV) ?? Van de Graaff
accelerator (protons up to 10 MeV) ?? Tandem Van
de Graaff accelerator (protons up to 20 MeV) ??
resonance accelerators ?? cyclotron (protons up
to 25 MeV) ?? linear accelerators electron
linac 100 MeV to 50 GeV ??
proton linac up to 70 MeV ??
synchronous accelerators ?? synchrocyclotron
(protons up to 750 MeV) ?? proton synchrotron
(protons up to 900 GeV) ?? electron synchrotron
(electrons from 50 MeV to 90 GeV) ??Induction
Induction linac, betatron
35
electrostatic accelerators generate high
voltage between two electrodes ? charged
particles move in electric field, energy gain
charge times voltage drop Cockcroft-Walton and
Van de Graaff accelerators differ in method to
achieve high voltage.
36
Cockroft-Walton

• High voltage source using rectifier units
• Voltage multiplier ladder (made of diodes and
  capacitors) allows reaching up to 1 MeV
  (sparking).
• First nuclear transmutation reaction achieved in
  1932 p 7Li ? 24He
• CW was widely used as injector until the
  invention of RFQ

Fermilab 750 kV C-W preaccelerator
37
Van de Graaff

• Voltage buildup by mechanical transport of
  charge using a conveyor belt. up to 20 MV

The charged particles are extracted from an ion
source housed inside the high-voltage terminal
and accelerated down an evacuated tube to ground
potential.
38
Tandem Van de Graaff

• Negative ions accelerated towards a positive HV
  terminal, then stripped of electrons and
  accelerated again away from it, doubling the
  energy.
• Negative ion source required!

39
The Million Volt BarrierSummary of Problems in
getting HV 1929

• Voltage Generators
• Insulators 750 kV max holding !
• Power
• Safety in using HV
• Funding
• Imagination

40
RF Accelerators
Radiofrequency oscillating voltage

• High voltage gaps are very difficult to maintain
• Solution Make the particles pass through the
  voltage gap many times!
• First proposed by G. Ising in 1925
• First realization by R. Wiederöe in 1928 to
  produce 50 kV potassium ions
• Many different types

41
RF LINAC basic idea

• Particles accelerated between the cavities
• Cavity length increases to match the increasing
  speed of the particles
• EM radiation power P ?rfCVrf2
• the drift tube placed in a cavity so that the EM
  energy is stored.
• Resonant frequency of the cavity tuned to that of
  the accelerating field

42
RF LINAC phase focusing

• E. M. McMillan V. Veksler 1945
• The field is synchronized so that the slower
  particles get more acceleration

43
1.Accelerators

• History-Why
• Particle Sources
• Acceleration stage
• Space charge
• Diagnostics
• Application

44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
50
1.Accelerators

• History-Why
• Particle Sources
• Acceleration stage
• Space charge
• Diagnostics
• Application

51
What do you want to know about the beam?

• Intensity (charge) (I,Q)?
• Position (x,y,z)?
• Size/shape (transverse and longitudinal)?
• Emittance (transverse and longitudinal)?
• Energy
• Particle losses

52
Properties of a charged beam

• Almost all accelerators accelerate charged
  particles which interact with matter.
• That's almost all what you need to use to build
  diagnostics (together with some clever tricks).

53
Faraday cup (1)?

• Let's send the beam on a piece of copper.
• What information can be measured after the beam
  has hit the copper?

54
Faraday cup (2)?

• Two properties can be measured
• Beam total energy
• Beam total charge
• By inserting an ammeter between the copper and
  the ground it is possible to measure the total
  charge of the beam.
• At high energy Faraday cups can be large More
  than 1m at Diamond.

Image source Pelletron.com
55
Beam current monitor

• Remember as the charge travelling in the beam
  pipe is constant the current induced on the walls
  (of the beam pipe) will be independent of the
  beam position.
• By inserting a ceramic gap and an ammeter the
  total charge travelling in a beam pipe can be
  measured.

56
Beam current monitor vs Faraday cup

• Both devices have pros and cons.
• A Faraday cup destroys the beam but it gives a
  very accurate charge measurements
• A Beam current monitor does not affect the beam
  but must be calibrated.
• Both tend to be used at different locations.

57
Screen (1)?

• If a thin screen is inserted in the path of the
  particles, they will deposit energy in the
  screen.
• If this screen contains elements that emit light
  when energy is deposited then the screen will
  emit light.
• Example of such elements Phosphorus, Gadolinium,
  Cesium,...

58
Screen (2)?

• It is not possible to stay in the accelerator
  while the beam is on so the screen must be
  monitored by a camera.
• To avoid damaging the camera the screen is at 45
  degrees.
• On this screen you can see both the position of
  the beam and its shape.
• Note the snow on the image.

59
Wire-scanner

• By inserting a thin wire in the beam trajectory
  (instead of a full screen) it is possible to
  sample parts of the beam.
• By moving the wire in the transverse direction
  one can get a profile of the beam.
• It is possible to use wire diameters of just a
  few micrometres.

60
Longitudinal properties

• It is not possible to directly image the
  longitudinal profile of a bunch.
• By giving longitudinal impulsion to the beam it
  is possible to make it rotate and observe its
  longitudinal profile.

61
Beam losses

• It is important to monitor the beam losses
  directly
• Small beam losses may not be detected by other
  systems
• Beam losses are a source of radiation and
  activation
• Most beam losses indicate that there is a problem
  somewhere.

62
Limitation of these monitors

• Monitors in which the matter interacts are prone
  to damage.
• With high energy high intensity colliders such
  damages are more likely to occur.
• To the left hole punched by a 30 GeV beam into
  a scintillating screen.

63
Laser-wire

• To mitigate the problem of broken wires in
  wire-scanners it is possible to replace the wire
  by a laser.
• This technique called laser-wire also allow to
  reach better resolutions.
• High power lasers (or long integration times) are
  needed.

64
Synchrotron radiation

• Synchrotron radiation carries information about
  the beam which emitted it.
• It is commonly used to study the beam shape.

65
Energy measurements

• To measure (or select) the energy of the
  particles a bending magnet is often the best
  solution.

66
Diagnostics overview
67
Summary

• There are two ways of measuring the properties of
  a beam
• By forcing it to interact with matter
• By looking at the EM radiation emitted.
• How to build the best diagnostic is then a matter
  of imagination!

68
1.Accelerators

• History-Why
• Particle Sources
• Acceleration stage
• Space charge
• Diagnostics
• Application

69
Several accelerator based methods can be used to
date old artefacts. Hospitals use accelerators
everyday to treat some forms of Cancer. The data
storage capacity of electronic devices has been
improved. The structure of molecules, including
drugs, can be studied with intense sources of
X-rays. Material hardness can be studied with
neutrons Intense flux of neutrons can burn
unwanted nuclear materials
70
Dating old artefacts
The Shroud of Turin
The shroud of Turin is a piece of cloth which was
first mentioned in the middle age. On it the face
of a man can be seen. Some claim that it is the
shroud that was used after the Christ's
crucifixion. In the 1980s 3 AMS laboratory
independently dated the sample they were provided
to 1260-1390.
71
(No Transcript)
72
Therapy
Comparison of the physical dose distribution
(upper diagram) and the survival rate of cells
(lower diagram) as a function of penetration
depth for ion and photon beams. The enhanced
energy deposition at the end of the particle
range and the corresponding dramatic decrease of
cell survival show that heavy ion beams are
excellent tools for the treatment of deep seated
tumours.
73
therapy
74
Sub-micron micromachining interactions

• Masked processes (electromagnetic)
• Light
• X-rays

• Direct write processes
• Electrons
• Low energy heavy ions (eg gallium)
• High energy light ions (protons)

75
Proton Beam Micro-machining
FDSPM
76
(No Transcript)
77
Pharmaceutical drugs
To be efficient a drug need to target the correct
molecule. This can only be achieved by studying
the diffraction of intense on the molecule. What
type of machine (gun, accelerator, ...) is best
suited to deliver an intense stable beam of
X-rays?
78


Fig.2.3 Schematic drawing of electrostatic
storage ring (ELISA).
79
HIRFL-CSR?????????????? ???????
????????
??2
??? ?????
??1
????
?
??? ????
?
HIRFL
ECR?
?
????
????
?
????
?
??
?
?????,??????
79
80
?????
????? ??? ??????
2008-2011,?????????
?????45??? ????????? ?????????? ????????????? ????
?????????
????????????????????????,??????????????????
80
81

• Producer
• Wuxi EL PONT Accelerator Research Institute ????
• http//www.elpont.net/abfs/EN/
• HV High Voltage Engineering Europa B.V.
  http//www.highvolteng.com/
• National Electrostatics Corporation (NEC)
• http//www.pelletron.com/index.html
• Kobelco
• http//www.kobelco.co.jp/english/machinery/product
  s/function/hrbs/index.html
• IBA
• http//www.iba-industrial.com/e-beam-accelerators

82
Jobs and graduate studies
Accelerators do not operate on their own. A
team is needed to manage the accelerator
operations. All accelerators facilities have a
wide-range of staff at all levels. There are
also many jobs connected to the usage of
accelerators. New machines bring new challenges
and there are many opportunities for graduate
studies in Accelerator science.
83

• Timothy Koeth
• Physics, Oxford University
• www-w2k.gsi.de/charms/Talks/CHARMS/
• Greg LeBlanc
• ???
• ??