Beam monitoring using Optical Transition Radiation (OTR) M.Sc. - - PowerPoint PPT Presentation

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Beam monitoring using Optical Transition Radiation (OTR) M.Sc. - - PowerPoint PPT Presentation

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Beam monitoring using Optical Transition Radiation (OTR) M.Sc. Tiago Fiorini da Silva tfsilva@if.usp.br Laboratrio do Acelerador Linear (LAL) Linear Accelerator Laboratory Laboratrio de Implantao Inica (LIO) Ion Implantation

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SLIDE 1

June 10th, 2010 - TFS 1

Beam monitoring using Optical Transition Radiation

(OTR)

M.Sc. Tiago Fiorini da Silva

tfsilva@if.usp.br

Laboratório do Acelerador Linear (LAL)

Linear Accelerator Laboratory

Laboratório de Implantação Iônica (LIO)

Ion Implantation Laboratory

Instituto de Física da Universidade de São Paulo

Physics Institute of the University of São Paulo

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SLIDE 2

June 10th, 2010 - TFS 2

Abstract

  • Optical Transition Radiation (OTR) has been used

for diagnostic purposes in particle beams for several reasons. For instance, linearity with beam current, polarization, spectrum and time of formation are all characteristics that make OTR an excellent tool to monitor beams in a wide range of

  • energies. It will be presented how OTR plays this

important role for a complete beam characterization, as well as some experimental data from an OTR based tool used for the diagnostic of low energy and low current electron beams of the IFUSP Microtron.

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SLIDE 3

June 10th, 2010 - TFS 3

Summary

  • Introduction

Theoretical background Transition Radiation characteristics

  • OTR used in beam diagnostics

Examples of uses of OTR in beam diagnostics When is an OTR based diagnostic device necessary?

  • The OTR based tool for the IFUSP Microtron

IFUSP Microtron facilities Design & Experimental data

  • Conclusions
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SLIDE 4

June 10th, 2010 - TFS 4

Introduction

  • Theoretical background
  • Main characteristics
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SLIDE 5

June 10th, 2010 - TFS 5

Introduction

Theoretical background Definition:

  • When a particle travels with constant velocity and

crosses the boundary between two media with different electromagnetic properties, it emits radiation with particular angular distribution, polarization and spectra. Predicted by Ginzburg and Tamm in 1946. Firstly observed by Goldsmith and Jelley in 1959.

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SLIDE 6

June 10th, 2010 - TFS 6

Introduction

Theoretical background In the limit case of a particle incident on a perfect conductor infinite plane:

  • +

Real charge Virtual charge v

  • v

Before hitting

In this case the boundary condition ‘creates’ a virtual charge inside the media.

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SLIDE 7

June 10th, 2010 - TFS 7

Introduction

Theoretical background In the limit case of a particle incident on a perfect conductor infinite plane:

Real charge v After hitting

In this case the perfect conductor completely suppresses the particle electromagnetic field.

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SLIDE 8

June 10th, 2010 - TFS 8

Introduction

Theoretical background

This sudden variation in the electromagnetic field induces to emission of radiation.

  • Differently to Cherenkov radiation, transition radiation
  • ccurs to any particle velocity.
  • Differently to Bremstralung radiation, transition radiation

does not vanishes to infinite particle mass.

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SLIDE 9

June 10th, 2010 - TFS 9

Introduction

Theoretical background

The angular distribution in the plane containing the vector

  • f the particle velocity and the normal to the surface is

given by:

( ) ( )

2 3 2 2 2 2

cos 1 sin 2 cos 1 2 sin 2

  • −

+

  • −

+ − ⋅

  • =

Ω θ θ ϕ θ ϕ θ π ω c v c v c v e d d W d

0.2 0.4 0.6 0.8 1 30 210 60 240 90 270 120 300 150 330 180 OTR emission Surface 0.2 0.4 0.6 0.8 1 30 210 60 240 90 270 120 300 150 330 180 OTR emission Surface 0.2 0.4 0.6 0.8 1 30 210 60 240 90 270 120 300 150 330 180 OTR emission Surface

2 MeV 5 MeV 10 MeV

Important in the OTR device design!

Beam Beam Beam

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SLIDE 10

June 10th, 2010 - TFS 10

Introduction

Main characteristics

The radiation spectra is continuum Limit of perfect conductor model:

  • Intensity is strongly attenuated

near the plasma oscillation wavelength

Obs.: for metals the plasma oscillation wavelength is of order of 10 nm in the visible range (300-1000 nm) the perfect conductor is a good approximation.

  • F. Sakamoto, et. al - Emittance and energy measurements
  • f low-energy electrons beam using optical transition

radiation techniques, JJAP vol.44, 3, 2005, 1485-1491.

  • −
  • =

1 ln 2

pe photon

d dN λ γλ πλ α λ

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SLIDE 11

June 10th, 2010 - TFS 11

Introduction

Main features

  • Characteristic polarization (will be seen later)
  • It is linear with the incident charge (no saturation)
  • The time of formation is too short (no mean time)
  • Initial phase (coherency capabilities)
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SLIDE 12

June 10th, 2010 - TFS 12

OTR used in beam diagnostics

  • Examples of uses of OTR in beam diagnostics
  • When is an OTR based diagnostic device necessary?
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SLIDE 13

June 10th, 2010 - TFS 13

OTR used in beam diagnostics

Single foil OTR measurement

This method consists of

  • bserve the radiation

emitted by charges in the transition of a single surface.

  • C. B. Reid - Measurement of electron beam emittance using optical

transition radiation and development of a diffuse screen electron beam monitor, Doctorate thesis, Naval Postgraduate School, Monterey, California.

Modes of operations

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SLIDE 14

June 10th, 2010 - TFS 14

OTR used in beam diagnostics

Single foil OTR measurement

Modes of operation

  • R. B. Fiorito and D. W. Rule - Optical transition radiation beam emittance diagnostics, AIP/BIW, vol 319, 21-37.

Near field

  • bservation

Far field

  • bservation

Far field observation of the horizontal polarization

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SLIDE 15

June 10th, 2010 - TFS 15

OTR used in beam diagnostics

Single foil OTR measurement

  • The angular distribution brings the information of the beam

energy and divergence.

  • The peak position is

inversely proportional to the beam energy.

  • The observed image

is a convolution of the emission of a single electron and the beam divergence distribution.

  • F. Sakamoto, et. al - Emittance and energy measurements of low-energy electrons

beam using optical transition radiation techniques, JJAP vol.44, 3, 2005, 1485-1491.

Vertical polarization of OTR image of 22 MeV electrons

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SLIDE 16

June 10th, 2010 - TFS 16

OTR used in beam diagnostics

Single foil OTR measurement

  • Resolution and systematic errors limits this method:
  • The value of beam

divergence interferes in the energy measurement

  • The value of beam

divergence is limited in the interval

  • f 1/ and
  • F. Sakamoto, et. al - Emittance and energy measurements of low-energy electrons

beam using optical transition radiation techniques, JJAP vol.44, 3, 2005, 1485-1491.

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SLIDE 17

June 10th, 2010 - TFS 17

OTR used in beam diagnostics

Single foil OTR measurement

As OTR is practically instantaneously formed, it can be used to measure beam variations as function

  • f time.

More important than that, OTR has time-resolved capabilities.

  • K. Tian, et. al – Fast imaging of time-dependent distribution of intense

beams, In: proceedings of PAC07, New Mexico, USA.

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SLIDE 18

June 10th, 2010 - TFS 18

OTR used in beam diagnostics

Double foil OTR measurement (OTR interferometer)

This method consists of analyzing the interference pattern of OTR emitted by two or more interfaces. Interferometer method has a higher resolution and no limitations on divergence measurements compared to the single foil method.

  • R. B. Fiorito and D. W. Rule - Optical transition

radiation beam emittance diagnostics, AIP/BIW, vol 319, 21-37.

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SLIDE 19

June 10th, 2010 - TFS 19

OTR used in beam diagnostics

Double foil OTR measurement (OTR interferometer) OTRI

  • R. B. Fiorito and D. W. Rule - Optical

transition radiation beam emittance diagnostics, AIP/BIW, vol 319, 21-37.

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SLIDE 20

June 10th, 2010 - TFS 20

OTR used in beam diagnostics

OTR + ODR interferometer OTDRI

This method consists of analyzing the pattern of interference between the transition radiation and diffraction radiation.

  • R. B. Fiorito, et.al - Interference of diffraction and transition radiation and its

application as a beam divergence diagnostic, PRST-AB, 9, 052802 (2006).

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SLIDE 21

June 10th, 2010 - TFS 21

OTR used in beam diagnostics

OTRI and ODTRI differences:

ODTRI OTRI

  • R. B. Fiorito, et.al - Interference of diffraction and transition radiation and its

application as a beam divergence diagnostic, PRST-AB, 9, 052802 (2006).

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SLIDE 22

June 10th, 2010 - TFS 22

OTR used in beam diagnostics

ODR + DTR + OTR interferometer

This method consists of analyzing the pattern of interference between the diffraction radiation and transition radiation of a thin transparent dialectical foil and a conductor foil.

  • R. B. Fiorito, et. al – Optical diffraction-dielectrical foil radiation interferometry

diagnostic for low energy beams, In: proc. of PAC07, New Mexico, USA.

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SLIDE 23

June 10th, 2010 - TFS 23

OTR used in beam diagnostics

Uses of coherent emission of OTR

This method consists of analyze the OTR spectra and by means

  • f a signal deconvolution it is

possible to measure the longitudinal charge distribution.

  • D. Mihalcea, et. al - Longitudinal electron bunch diagnostic using coherent

transition radiation, In: proceeding of PAC05, Tennessee, USA.

( ) ( ) ( ) ( ) ( ) ( )

  • ⋅

⋅ = ⋅ ⋅ − = dz c z i z f f I N N I

e

/ exp 1

2

ω ρ ω ω ω

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SLIDE 24

June 10th, 2010 - TFS 24

OTR used in beam diagnostics

When is an OTR diagnostic device necessary?

When there is a need for:

  • Time-resolved measurement;
  • High spatial resolution;
  • Measurement of many parameters in a single point;

Or:

  • When an optical instrumentation is preferred;
  • When the charge distribution need to be measured

(in substitution of phosphor screens);

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SLIDE 25

June 10th, 2010 - TFS 25

OTR used in beam diagnostics

As OTR is has a linear dependency with the incident charge, this process of radiation production has a great advantage

  • ver fluorescence.

The actual charge distribution can be measured.

  • A. Murokh, et. al - Limitations on measuring a transverse profile of ultra-dense

electron beams with scintillators, In: proc. of PAC01, Chicago, USA.

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SLIDE 26

June 10th, 2010 - TFS 26

OTR used in beam diagnostics

  • Granularities in the phosphor reduces the resolution of

spatial measurements;

  • OTR does not present any granularity;
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SLIDE 27

June 10th, 2010 - TFS 27

The OTR based tool for the IFUSP Microtron

  • IFUSP Microtron facilities
  • Design & Experimental data
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SLIDE 28

June 10th, 2010 - TFS 28

The OTR based tool for the IFUSP Microtron

IFUSP Microtron facilities

Schematic view

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SLIDE 29

June 10th, 2010 - TFS 29

The OTR based tool for the IFUSP Microtron

IFUSP Microtron facilities

Current status

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SLIDE 30

June 10th, 2010 - TFS 30

The OTR based tool for the IFUSP Microtron

IFUSP Microtron facilities

  • Atomic Research
  • Interaction of High Energy Electrons with Matter
  • Radiotherapy Research
  • Radiation Physics
  • Nuclear Resonance Fluorescence
  • Photonuclear Reactions
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SLIDE 31

June 10th, 2010 - TFS 31

The OTR based tool for the IFUSP Microtron

IFUSP Microtron facilities Needs for a diagnostic device:

  • Measurement of the actual charge distribution

before the sample chamber.

  • Phase space diagnostic before the microtron

booster.

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SLIDE 32

June 10th, 2010 - TFS 32

The OTR based tool for the IFUSP Microtron

  • OTR intensity is usually

low intense;

  • The main issue in the

design of an OTR device for 1.8 MeV is the low intensity and the spread angular distribution;

  • Our design has an

additional challenge: low current (µA~nA);

beam 45º incidence

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SLIDE 33

June 10th, 2010 - TFS 33

The OTR based tool for the IFUSP Microtron

  • In our design, the

solution adopted was to change the incidence angle in order to increase the radiation emitted in the camera direction;

  • A numerical integration

in the field of view indicates a intensity 150% higher then the 45º incidence case;

beam 38.5º incidence

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SLIDE 34

June 10th, 2010 - TFS 34

The OTR based tool for the IFUSP Microtron

  • The target holder corrects the angle of incidence.
  • The target consists of a silicon substrate coated

with a Aluminum film of 200 nm thick.

  • Silvered ink provide

electrical contact between the target and the holder, in

  • rder to avoid charge

concentration.

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SLIDE 35

June 10th, 2010 - TFS 35

The OTR based tool for the IFUSP Microtron

  • Our OTR device has a regular phosphor screen

mounted in right angle to perform beam positioning during the machine normal operation;

  • Two different

cameras are coupled to the windows;

Regular CCD camera to phosphor screen; Special CCD camera to OTR;

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SLIDE 36

June 10th, 2010 - TFS 36

The OTR based tool for the IFUSP Microtron

What is special about the OTR camera?

  • Adjustable shutter speed;
  • Adjustable gain;
  • Adjustable gamma correction;
  • Firewire connection;
  • Automatic sequence of shots;

AVT Guppy F-038B – Allied Vision

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SLIDE 37

June 10th, 2010 - TFS 37

The OTR based tool for the IFUSP Microtron

  • Provisional installation right after the

1.8 MeV linac injector.

  • A 45°dipole creates high dispersion

function at the monitor position to energy spread measurement.

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SLIDE 38

June 10th, 2010 - TFS 38

The OTR based tool for the IFUSP Microtron

  • First image with the device;
  • Many artifacts were found, however, there is a

suspicious OTR image;

  • Some tests makes necessary;
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SLIDE 39

June 10th, 2010 - TFS 39

The OTR based tool for the IFUSP Microtron

  • First image with the device;
  • Many artifacts were found, however, there is a

suspicious OTR image;

  • Some tests makes necessary;

Fluorescence of the vacum glue (unexpected); Dust in the vacum window; OTR? If yes: Low energy electrons; The beam;

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SLIDE 40

June 10th, 2010 - TFS 40

The OTR based tool for the IFUSP Microtron

Test 1 – Linearity Test performed with the variation of the beam repetition rate. Each point represents a time integration

  • ver 1 sec.

50 100 150 200 250 300 350 0,0 1,0 2,0 3,0 4,0

Current (nA) Intensity (a.u.)

Experimental data Linear fitting

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SLIDE 41

June 10th, 2010 - TFS 41

The OTR based tool for the IFUSP Microtron

Test 2 – Polarization Test performed with the variation of the angle of a polarizer in a goniometer;

60 80 100 120 140 160 180

  • 250
  • 200
  • 150
  • 100
  • 50

50 100 150 200 250

Angle (º) Intensity (a.u.)

Experimental data Fitting

(a) (b)

Goniometer

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SLIDE 42

June 10th, 2010 - TFS 42

The OTR based tool for the IFUSP Microtron

  • Charge distribution measurement
  • As the OTR is linear dependent to the incident charge, the observed image

corresponds to the charge distribution

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SLIDE 43

June 10th, 2010 - TFS 43

The OTR based tool for the IFUSP Microtron

  • Energy spread measurement
  • Energy spread may be measured in a point of the accelerator where the

dispersion function has a value much higher than the beam radius.

( )

  • ⋅

= = − − + − = ⋅ = ∆ dl s B B l l L L L D x L D p p

ef ef

1 and where ) cos 1 ( tan sin ) cos 1 ( ) ( ) ( θ ρ θ δ θ θ ρ

23.5-cm

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SLIDE 44

June 10th, 2010 - TFS 44

The OTR based tool for the IFUSP Microtron

Beam before the dipole Beam after the dipole

  • Energy spread measurement
  • Some illustration with simulated data.

23.5-cm

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SLIDE 45

June 10th, 2010 - TFS 45

The OTR based tool for the IFUSP Microtron

0,00 0,02 0,04 0,06 0,08

  • 0,010
  • 0,005

0,000 0,005 0,010

dp/p0 Intensity (a.u.)

Intensity Gaussian fitting

3

10 . 8 , 1

−

= ∆

HWHM

p p

  • Energy spread measurement
  • The beam energy distribution

was measured;

  • The energy distribution

has a gaussian shape with a little longer tail in the lower energies region;

  • Data used to optimize the

chopper/buncher system;

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SLIDE 46

June 10th, 2010 - TFS 46

The OTR based tool for the IFUSP Microtron

  • Emittance measurement
  • Some illustrative data

Quad scan method = 1.6 .mm.mrad

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SLIDE 47

June 10th, 2010 - TFS 47

The OTR based tool for the IFUSP Microtron

Some innovative measurement:

  • Use of incoherent radiation to measure bunch length;
  • Dr. Sannibale et. al, showed the viability of the use of

incoherent synchrotron radiation;

  • We intend to use incoherent

OTR to the same purpose;

  • F. Sannibale, et. al – Absolute bunch length measurements by incoherent

radiation fluctuation analysis, PRST-AB 12, 032801, 2009.

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SLIDE 48

June 10th, 2010 - TFS 48

The OTR based tool for the IFUSP Microtron

  • OTR intensity is measured integrating the intensity

in the image (extracting background)

  • Many measurements are required (uncertainty

goes with the inverse square root of the number of samples)

Beam OTR Optical filter Camera

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SLIDE 49

June 10th, 2010 - TFS 49

The OTR based tool for the IFUSP Microtron

  • Preliminary measurements indicates a fluctuation of the

OTR intensity;

  • Calculating the bunch length it is found 3,1 ps (2.6º).
  • Simulations of the linac injector with the PARMELA code

indicates a bunch length in the linac exit of 2º.

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SLIDE 50

June 10th, 2010 - TFS 50

Conclusions

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SLIDE 51

June 10th, 2010 - TFS 51

Conclusions

  • OTR based diagnostic devices are very versatile
  • Allow the measurement of many beam characteristics in a

single point

  • Very high resolution measurements can be achieved
  • Time-resolved measurements can be performed
  • Construction is relatively simple
  • Can be used in low energies with restrictions of

applicability

  • The actual transverse charge distribution can be obtained
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SLIDE 52

June 10th, 2010 - TFS 52

Acknowledgements

  • Dr. Marcos Martins (advisor)
  • Dr. Vito Vanin (LAL director)
  • Dr. Paulo Pascholati
  • Ms. Cristiane Jahnke

Technical staff:

  • Dr. Alexandre Malafronte
  • Mr. Alex Silva
  • Dr. Alfredo Bonini
  • Mr. Luciano Portante
  • Mr. Marcelo Lucena
  • Dr. Roberto Lima

Contributors:

  • Dr. Ralph Fiorito
  • Dr. Fernando Sannibale

Target manufacturing:

  • Dr. Roberto Onmori (LME-POLIUSP)

M.Sc. Celso Silva (LME-POLIUSP)

Target characterization:

  • Dr. Manfredo Tabacniks (LAMFI-IFUSP)
  • Dr. Nemitala Added (LAMFI-IFUSP)
  • Dr. Marcel Dupret (LAMFI-IFUSP)

Optical filter

  • Dr. Marcelo Martineli (LMCAL-IFUSP)

Financial support: contact: tfsilva@if.usp.br