Title page

INDICE

Preface

Gruppo fotografico dei partecipanti al Corso

Experiments with many-positron systems

Introduction

Positron accumulation

Positron beam

Positron accumulator

Positron plasma compression

Production and detection of intense positron pulses

Single-shot positron annihilation lifetime spectroscopy

Fast detectors

Lead tungstate: PbWO4

Lead fluoride: PbF2

Spatiotemporal compression

Experiments with intense positron pulses

Positronium formation in porous materials

Ps diffusion

Ps cooling

Laser spectroscopy of positronium

Interactions between positronium atoms

The effect of Ps-Ps quenching on lifetime spectra

Spin exchange quenching

Molecular positronium formation

Positronium as a probe of transient phenomena

Concluding remarks and future work

Physics with many positrons

Physics with many positrons

Introduction

Last of the polyelectrons

Observation of positronium molecules

Dreams of the gamma-ray laser

Many-positron physics

Many-positron states

Introduction

Positron surface states

Many positrons in a solid

Ps-Ps Scattering and Ps2 molecule formation from Ps surface states

Ps2 formation interaction radius for dense positronium (Ps) on an insulator surface

Scattering states of two Ps atoms with given total spin angular momentum

Model for thermal inactivation of Ps2 formation in porous silica

Model for thermal dissociation of Ps2 in a cavity neglecting wall interactions

Thermal desorption of positronium from an insulator surface

Neutral plasmas

Low density e+-e- plasmas

Long-term storage of low-density neutral electron-positron plasmas

Thermalization of the positrons and electrons

High density e+-e- plasmas

Positronium Bose-Einstein condensation

Introductory material

Identical particles

Consequences of particle identity

Stimulated emission

Formation of polarized positronium

Laser cooling of positronium

Introduction

Pulsed laser cooling

Sub-recoil cooling

BEC physics

Introduction

Importance of positronium Bose-Einstein condensation

Approach to thermal equilibrium in a Ps BEC

Approach to phase coherence in a Ps BEC

Effects of a fixed random potential

BEC in alternate geometries

Introduction

Condensation

Spin exchange quenching

Special geometries

Superfluidity

Optical experiments on positronium

Motivation for measurements on antimatter

Inducing triplet-to-singlet transitions in positronium

Ground-state hyperfine transitions

Triplet-singlet mixing via a pulsed magnetic field

Laser requirements for experiments on positronium

Laser excitation of Ps 1S-2P transitions in vacuum

Measurement of the 1So to 1Pe interval of Ps2

Laser cooling of a cloud of Ps atoms

Photograph the Ps molasses

Measurement of the first-order Doppler-free cold Ps 1S-2S linewidth

First-order Doppler-free two-photon (452 nm) measurement of the 1So to 1So* interval of Ps2

Laser cooling of Ps atoms confined in a small cavity

Formation of a laser-cooled positronium Bose-Einstein condensate (BEC) in a cavity

Optical observations of cavity positronium

Observation of the Bose-Einstein condensation of positronium

Demonstration of positronium tunneling into vacuum

Other experiments

Laser spectroscopy of di-positronium molecules

Experiments on positronic compounds

Stimulated annihilation and the annihilation gamma-ray laser

Introduction

Why would one wish to make a gamma-ray laser?

Why is an annihilation laser possible?

Details of the Ps BEC ground state

Positron sources

Isotope separation of 79Kr

Space charge limit to the focusing of a cylindrical current

Space charge limit to the focusing of a flat sheet of current

An annihilation laser requires a slow-positron line focus in zero field

Heat dissipation

Thresholds for stimulated emission and lasing

Fusion

Deposition of gamma-ray energy in a DT plasma

Fusion threshold

Power generation

Appendix A. Problems

Antihydrogen physics

Introduction

Motivation for antihydrogen experimentation

The CPT theorem

Gravity

Introductory Penning trap and plasma physics

The Penning trap

Plasma physics

Antiparticle trapping and manipulation for antihydrogen

Antiproton trapping and cooling

Antiproton stacking and manipulation

Positron trapping and manipulation

Positron accumulator-operational issues

Antihydrogen formation

Mechanisms

Positron-antiproton mixing in a nested trap and antihydrogen formation

Field ionization of antihydrogen

Insights from simulations

Antihydrogen trapping

The magnetic minimum neutral trap-general considerations

Plasma stability in multipolar magnetic fields

The ALPHA antihydrogen trap

Concluding remarks

Antihydrogen production in the ATHENA apparatus

Introduction

Experimental data

Conclusions

Towards antihydrogen spectroscopy

Introduction

Tests of the symmetry between matter and antimatter

Laser spectroscopy of the 1 S-2 S transition

Ultrahigh-resolution laser spectroscopy using ordinary hydrogen atoms

Towards laser spectroscopy of antihydrogen

Microwave spectroscopy of the hyperfine splitting

Beyond antihydrogen spectroscopy

Conclusions

Positronium emission and cooling

Introduction

Positronium emission from solids

Positronium emission from metals

Positronium formed by backscattered positrons

Positronium formed by epithermal positrons

Direct positronium formation by thermal positrons

Thermal emission of positronium

Positronium emission from dielectrics

Small band gap dielectrics

Large band gap dielectrics

Positronium thermalization and cooling

Ps emission at low temperature from modified metal surfaces

Collisional cooling of Ps (theory)

Collisional cooling of Ps (experiments)

Ps cooling in gases

Ps cooling in silica powders

Ps cooling at room temperature in silica-based porous materials

Ps formation and cooling in ordered nano-channels

Ortho-positronium quenching by pick-off and spin exchange in silica-based materials at cryogenic temperature

Concluding remarks

Positronium for antihydrogen production

Introduction

Materials for positron-ortho-positronium conversion

Characterization of the films by lifetime spectroscopy

Determination of the energy of emitted o-Ps by time-of-flight spectroscopy

Intense slow-positron source using a linear electron accelerator

Concluding remarks

Laser-driven positronium excitation in the AEGIS antimatter experiment at CERN

Introduction

The physics of AEGIS

The production of the antihydrogen beam

Ps formation

Antihydrogen formation and acceleration

The gravity measurement

Positronium laser excitation: theory of Rydberg level structure of moving Ps in strong magnetic fields

Zeeman energy splitting Delta EZ

Diamagnetic energy splitting Delta Edia

Motional Stark (MS) energy splitting Delta EMS

Positronium laser excitation: tailoring pulse energies and bandwidth

Fluence of laser pulses for low-n excitations

Fluence of laser pulses for Rydberg level excitations

Laser pulse energies and excitation efficiency

Conclusions

Appendix A. Definition of saturation fluence

Compounds of positrons with koino-atoms and -molecules

Introduction

The meaning of "stability"

Chemical formulas and nomenclature; electronegativity

Feynman diagram for annihilation and its consequences

Time scales and their consequences

Structural formulas

Appropriate quantum mechanics

Structure of mixed electron-positron systems

The correlation problem

Angular momentum coupling

The orbital picture

Mechanisms for binding positrons and positronium

Positron binding

Positronium binding

Theory and experiment

Theory

The calculation of annihilation rates

The configuration interaction method as applied to atoms

The stochastic variational method

The quantum Monte Carlo method

CI as applied to large molecules

Current experimental methods

Red shifts of vibrational spectral features

Dissociative attachment

Present knowledge

Polyleptons

Atoms in their ground states

Molecules in their ground states

Theoretical work

Experimental work

Excited states

PsH

e+He* (2;3Se and 4;3Se)

The 2;3Po and 4;3Po states of e+Be

e+Ca (2;1Po)

The (np22p) 2;3So and 4;3So states of PsH (n = 2) and NaPs (n = 3)

Systems with more than one positron

The past: Older experimental results

Appendix A. Data tables

Positron sources and positron beams

Introduction

Production of positrons

Positron beams based on beta+ decay

beta+ emitter

Positron moderation

Table-top positron beams

Positron beams based on pair production

The pair production process

Bremsstrahlung targets at linacs

Reactors

Future bright gamma sources

The positron beam facility NEPOMUC

The in-pile positron source

Positron beam facility

The positron instrumentation

NEPOMUC as user facility

Pulsed low-energy positron beams in materials sciences

Introduction

The Pulsed Low Energy Positron Beam System (PLEPS)

The entrance section

The pulsing section

The Prebuncher

The Chopper

The Main Buncher

The acceleration stage

The target chamber

Performance of PLEPS

The Scanning Positron Microscope (SPM)

Basic problems of positron microscopy

SPM

The primary beam

The remoderator section

The optical column

Performance and future developements

Defect profiling with pulsed positron beams

Applications

Defect-free case

Defect investigations using the back-diffusion method

Combined use of PLEPS and SPM

Defect profiling in thin layers

Limits

Depth resolution

Lateral resolution

Determination of absolute concentrations

Pulsing with many positrons

Concluding remarks

Current intense positron beams at the North Carolina State University PULSTAR reactor and Argonne National Laboratories

Introduction

The NCSU PULSTAR Reactor Positron Beam

The Argonne National Laboratory LINAC Beam

Intense positron beams in the U.S., past and future

The EPOS system at the radiation source ELBE at Forschungszentrum Dresden-Rossendorf

Introduction

MePS (Mono-energetic Positron Spectroscopy)

The timing system

Radiation protection

Gamma-induced Positron Spectroscopy

Producing bremsstrahlung at ELBE

The GiPS setup

Characteristics of the GiPS facility and first examples

Positron generation with small accelerators

Relativistic positron creation using ultra-intense short-pulse lasers

Introduction

Basic theory and modeling of laser electron acceleration and pair creation

Experimental setup

Positron detection methods

Direct positron measurement

Positron measurement through annihilation photons at 0.511 MeV

Positron energy spectrum

Positron angular distribution

Data modeling

Future work

Accumulation, storage and manipulation of large numbers of positrons in traps I. - The basics

Overview

Positron trapping

Background and overview

An efficient accumulation scheme: the buffer gas trap

Positron cooling

Collisional cooling using atomic or molecular gases

Cyclotron cooling

Sympathetic cooling using ions

Confinement and characterization of positron plasmas in Penning-Malmberg traps

Basic concepts

Transport due to neutral collisions

Transport due to electric and magnetic asymmetries

Plasma heating

If neutral collisions dominate both the transport and the cooling

Diagnostic techniques

Radial compression using rotating electric fields: the "rotating wall" technique

Rotating-wall compression in the single-particle regime

Heating due to rotating-wall compression

Maximum achievable density using RW compression

Concluding remarks

Accumulation, storage and manipulation of large numbers of positrons in traps II. - Selected topics

Overview

Extraction of beams with small transverse spatial extent

Multicell trap for storage of large numbers of positrons

Overview

Validation of the multicell trap concept

Summary

Electron-positron plasmas

Combined trap for low-density electron-positron plasmas

Magnetic-mirror confinement of hot electron-positron plasmas

Confinement in a Stellarator

Concluding remarks

The simulation of moderated positrons behavior in a micro-trap with long aspect ratios

Overview

Introduction

Simulation description

Results

The effect of the initial position

The effect of magnetic fields

The effect of the initial angle

Space charge effect

The tube size effect

The effect of the initial energy

Variable potential on the boundary

Multiple runs with loop program

Multiple runs with space charge and variable potential

Summary

Elenco dei partecipanti