High Efficiency Cyclotron Trap Assisted Positron Moderator

Lars Gerchow,Paolo Crivelli,David Cooke,Klaus Kirch,Tommaso Carzaniga,Christiaan Vermeulen,André Rubbia,Saverio Braccini,Nicholas Van Der Meulen,Arnold Müller,Max Döbeli,Ulli Köster

doi:10.3390/instruments2030010

Lars Gerchow, Paolo Crivelli + Show 10 more

Open Access

https://doi.org/10.3390/instruments2030010

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Abstract

We report on the realisation of a cyclotron trap assisted positron tungsten moderator for the conversion of positrons with a broad keV–few MeV energy spectrum to a mono-energetic eV beam with an efficiency of 1.8(2)% defined as the ratio of the slow positrons divided by the β+ activity of the radioactive source. This is an improvement of almost two orders of magnitude compared to the state of the art of tungsten moderators. The simulation validated with this measurement suggests that, using an optimised setup, even higher efficiencies are achievable. A novel method for the production of 48V high-activity thin foil positron sources based on a solid target station at a medical cyclotron was developed. This is an improvement of more than one order of magnitude with respect to standard methods.

Highlights

The positron and its bound state with an electron, positronium, have found many applications in physics and chemistry [1,2]
We present a scheme based on cyclotron trap assisted moderation that improves the amount of positrons available for the moderation process resulting in a higher efficiency
The division of the counts in the extraction mode by the total positron activity gives a moderation efficiency of of e = 1.8(2)% in fair agreement with what has been estimated from the simulation results

Summary

Introduction

The positron and its bound state with an electron, positronium, have found many applications in physics and chemistry [1,2] In medicine, they are used for what is probably the best known application of anti-matter in “everyday" life, the method of positron emission tomography (PET) [3]. They are used for what is probably the best known application of anti-matter in “everyday" life, the method of positron emission tomography (PET) [3] Relying on their unique sensitivity to the electronic environment, positrons serve in applied science for the characterisation of materials. We present a scheme based on cyclotron trap assisted moderation that improves the amount of positrons available for the moderation process resulting in a higher efficiency

Principle of the Cyclotron Trap Assisted Moderation

Thin Foil Positon Source

Experimental Setup

Simulation

Results

Conclusions

Methods