slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Applications of Caesium Iodide in High Energy Physics PowerPoint Presentation
Download Presentation
Applications of Caesium Iodide in High Energy Physics

Loading in 2 Seconds...

play fullscreen
1 / 17

Applications of Caesium Iodide in High Energy Physics - PowerPoint PPT Presentation


  • 157 Views
  • Uploaded on

Applications of Caesium Iodide in High Energy Physics. Applications of Caesium Iodide in High Energy Physics. What is Caesium Iodide?. Alkali Halide Scintillator Grown from crystal seed Fantastic light output Properties enhanced by dopants (Thallium or Sodium) - CsI(Tl).

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Applications of Caesium Iodide in High Energy Physics' - chill


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
applications of caesium iodide in high energy physics
Applications of Caesium Iodidein High Energy Physics

What is Caesium Iodide?

  • Alkali Halide Scintillator
  • Grown from crystal seed
  • Fantastic light output
  • Properties enhanced by dopants (Thallium or Sodium) - CsI(Tl)

Unfortunately CsI(Tl) is...

  • Prone to radiation damage
  • A Poison

A Caesium Iodide crystal from the BaBar calorimeter

applications of caesium iodide in high energy physics3
Applications of Caesium Iodidein High Energy Physics

What is Poison?

  • Piss-poor US rock/metal
  • Big hair (4 counts)
  • Still living in the 80’s
  • Leather and Denim fetishists

We proved in tests…

…music has same artistic value as a Polo mint

applications of caesium iodide in high energy physics4
Applications of Caesium Iodidein High Energy Physics

Poison’s artistic merit

Jimi Hendrix

Comfortably mediocre

Artistic Merit (log scale)

Krankies

Nowt

Arsecockfuck

applications of caesium iodide in high energy physics5
Applications of Caesium Iodide in High Energy Physics

What is a scintillator?

All solids give off energy as thermal radiation, normally in the infrared range. Some solids have the special capability of emitting ultra-violet and visible

radiation - when the excitation of the crystal is by charged particles or photons, the luminescent material is called a scintillator. Energy loss in scintillators is through the usual shower deposition process.

g

e-

e-

g

e+

g

e+

g

e-

e-

e-

e+

g

Radiation Lengthsc0

e-

0

1

2

3

applications of caesium iodide in high energy physics6
Applications of Caesium Iodide in High Energy Physics

The process of scintillation

Energy absorption from shower is by sensitiser. Photon emission is by activator. In some scintillators, a dopant is added to the lattice as a second activator to hinder re-absorption of photons - this is the role of the Thallium in CsI(Tl).

Electrons

Conduction Band EC

Exciton Band EE

Excitation

Photon emission

Photon absorption

Exciton creation

Exciton remains bound until

de-excited

De-excitation

Valence Band EV

Holes

applications of caesium iodide in high energy physics7
Applications of Caesium Iodide in High Energy Physics

Caesium Iodide - the John Shaft of scintillators

Not only is CsI(Tl) the black private dick that’s a sex machine to all the chicks, it is also the cat that won’t cop out when there’s danger all about.

=

applications of caesium iodide in high energy physics8
Applications of Caesium Iodide in High Energy Physics

Applications of CsI(Tl)

3 main areas that utilise CsI(Tl) scintillator:

  • Electromagnetic Calorimetry
  • Medical: PET and CAT scanners
  • Industrial applications: x-ray scanners (scintillator on CCD, PMT or pin-diode)
applications of caesium iodide in high energy physics9
Applications of Caesium Iodide in High Energy Physics

CsI(Tl) for Calorimetry

CsI(Tl) very good for calorimetry at BaBar energies. CsI(Tl) is also used for the electromagnetic calorimeter of the Belle experiment in Japan - also looking at B-physics.

The BaBar

Detector

Cross-section of

BaBar Calorimeter

applications of caesium iodide in high energy physics10
Applications of Caesium Iodide in High Energy Physics

Medical Applications

2 main types: Positron Emission Tomography (PET) and Computed Axial Tomography (CAT). PET scans use positron emission from radioactive isotopes; CAT scans rely on direct x-ray detection.

PET image

CAT image

applications of caesium iodide in high energy physics11
Applications of Caesium Iodide in High Energy Physics

Commercial Uses of CsI(Tl)

Primary commercial use of scintillators is x-ray scanners, such as those used in airport baggage scanners e.g. Hilger Crystals produce CsI(Tl) arrays for Rapiscan baggage scanners.

CsI(Tl) strip

mounted on a

pin-diode array

Some freak’s luggage

applications of caesium iodide in high energy physics12
Applications of Caesium Iodide in High Energy Physics

What’s so pimp about CsI(Tl)?

  • High light output and efficiency
  • Light output peak at 565nm (good for PMT’s)
  • Light output enhanced by second activator (Thallium) - less re-absorption
  • Moderately dense (4.5 g/cm3 - PbWO4 is just over 8 g/cm3) but fine for MeV-GeV energies
  • Slightly hygroscopic so crystals are water tuneable
applications of caesium iodide in high energy physics13
Applications of Caesium Iodide in High Energy Physics

Why CsI(Tl) doesn’t ask for trouble, but ends up getting glassed

2 main phenomena which affect performance of CsI(Tl):

  • Radiation Damage
  • Afterglow

Both phenomena are affected by doping concentration and crystal growing conditions; both hinder performance of crystal.

applications of caesium iodide in high energy physics14
Applications of Caesium Iodide in High Energy Physics

Radiation Damage: what’s the beef?

Continuous exposure to ionising radiation leads to the formation of colour centres (F-centres) - these colour centres absorb light in the blue/green, hence the reddish-brown hue of damaged/old crystals.

Cs+

I-

F-centre formation in CsI(Tl)

Scattered g

Incidentg

e

Captured electron

Scattered I- ion

applications of caesium iodide in high energy physics15

100ms

Applications of Caesium Iodide in High Energy Physics

Afterglow in CsI(Tl)

Afterglow in CsI(Tl) is not properly understood. Short term (ms) afterglow is important: high afterglow leads to smearing of measurements and degrades energy resolution.

Light output from a CsI(Tl) crystal with significant afterglow

applications of caesium iodide in high energy physics16
Applications of Caesium Iodide in High Energy Physics

Understanding Afterglow

System currently under construction for measuring afterglow in 1-inch CsI(Tl) plugs.

PC running LabVIEW

Incident x-rays

1.25 MHz ADC Card

BNC Adapter Box

Crystal and holder

PMT

applications of caesium iodide in high energy physics17
Applications of Caesium Iodide in High Energy Physics

And to conclude...

Caesium Iodide: not as accurate as it could be...