The York Bragg Detector – Design and Simulation James Butterworth Seminar at York 31/03/2010

Overview Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

1. BRAGG CURVE SPECTROSCOPY Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

Bragg Curve Spectrometry Idea suggested in 1982 by Gruhn et. al. “Conceptually BCS involves using the maximum data available from the Bragg curve of the stopping heavy ion for purposes of identifying the particle and measuring its energy.” Nuclear Instruments and Methods 196 (1982) 33-40

Typical Bragg Curves

From the Bragg Curve you can determine...  The range of the ion in the gas → A  The total area under the curve → E  The peak of the curve → Z TThe range of the ion in the gas → A TThe total area under the curve → E TThe peak of the curve → Z

How to analyse a Bragg Curve  Taking the peak height gives ΔE.  Integrating the full curve gives E.  Can create an E- ΔE plot.  Taking the peak height gives ΔE.  Integrating the full curve gives E.  Can create an E- ΔE plot.

A Typical Bragg Curve Spectrometer

2. THE YORK BRAGG DETECTOR Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

ISOLDE

Miniball

Contamination Issues  Isobaric contamination  A/q contamination  Contamination from radioactive decays in the beamline  Isobaric contamination  A/q contamination  Contamination from radioactive decays in the beamline Isobar

The Munich Bragg Detector  Situated at the end of the beam at Miniball, REX-ISOLDE.  An on axis Bragg detector for small sampling of the beam.  Designed and built at Technische Universität München.  Situated at the end of the beam at Miniball, REX-ISOLDE.  An on axis Bragg detector for small sampling of the beam.  Designed and built at Technische Universität München. Main drawbacks: 1.On axis so Miniball target must be removed in order to obtain data. 2.Due to detector response time only takes small sample of the beam. Main drawbacks: 1.On axis so Miniball target must be removed in order to obtain data. 2.Due to detector response time only takes small sample of the beam.

The York Bragg Detector  Off axis.  Allows concurrent monitoring of the beam.  Large acceptance.  Forms an annulus around the beamline.  Highly sensitive and selective.  Hope to achieve a Z resolution of 1/40.  Off axis.  Allows concurrent monitoring of the beam.  Large acceptance.  Forms an annulus around the beamline.  Highly sensitive and selective.  Hope to achieve a Z resolution of 1/40.

2.1 THE BRAGG VOLUME Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

Windows 5.486MeV Alpha Particle from 241 Am 241MeV 78 Sr Ion

Detector Gas W = Mean energy needed to create an ion pair Projectile = 90 Zr at 3.1 Mev/u, Gas pressure = 300 mbar

Frisch Grid Shielding Inefficiencyg = spacing between grid wires b α distance between grid & anode r = radius of the grid wires E C = Electric field in the collection volume E D = Electric field in the drift volume

Anode

Z-resolution Z resolution limited by:  Charge state fluctuations around Bragg peak  Z 2/3 dependence of Bragg peak Z resolution limited by:  Charge state fluctuations around Bragg peak  Z 2/3 dependence of Bragg peak Typical Z resolution = 1/40 1 2

2.1 THE PGAC Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

The Grids

The Gas and Field PGAC gas same as Bragg gas at 1/10 pressure

The Mechanical Elements

3. SIMULATIONS Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

Simulation Path SRIM/TRIM Garfield Matlab Preamplifier Simulation Result Data: Ions: 78 Sr and 78 Rb at 3.1 MeV/u Detector Gas: Propane at 100 mbar pressure Data: Ions: 78 Sr and 78 Rb at 3.1 MeV/u Detector Gas: Propane at 100 mbar pressure

SRIM vs TRIM TRIM Outputs – Text files containing data about the projectile, target layers, electromagnetic and nuclear energy loss, straggling etc. SRIM Outputs – Single table containing data about energy loss, penetration depth and straggling. Advantages of TRIM...  Simulates individual events  Allows multiple target layers  Number of ions and random seed can be selected  Deals with ionisation by ions and recoils

Introduction to Garfield  Simulation program. Simulates gaseous ionisation chambers.  Uses the best available approximations and techniques. Higher detail than Geant 4.  Garfield needs a description of the chamber and the gas as inputs.  Garfield then simulates the electron drift in the chamber, and the current induced on the chamber wires.  Simulation program. Simulates gaseous ionisation chambers.  Uses the best available approximations and techniques. Higher detail than Geant 4.  Garfield needs a description of the chamber and the gas as inputs.  Garfield then simulates the electron drift in the chamber, and the current induced on the chamber wires.

Garfield Inputs  Cell section  Gas section  Field section  Drift section  Signal section  Cell section  Gas section  Field section  Drift section  Signal section The chamber is described in this section.  Components are entered a 2D planes or wires, infinite in the third dimension.  Complex structures can be simulated using arrays of wires.  The dimensions of each component and voltages on them are specified here. The gas properties of the chamber are set here including...  Pressure.  Temperature.  Ion mobility.  Work function.  Fano factor.  SRIM file to be read in. The field drift and signal sections contain various commands for calculating and plotting the field, drift lines and induced current.

Garfield Outputs

The Garfield/SRIM Interface Garfield can interface with the SRIM quick range tables. It makes use of the values for...  Electromagnetic energy loss.  Nuclear energy loss.  Distance traversed by ions.  Longitudinal straggling.  Lateral straggling. For ions at a range of energies. Density of the gas is also read in. This replaces any value for density already read into Garfield. Garfield can interface with the SRIM quick range tables. It makes use of the values for...  Electromagnetic energy loss.  Nuclear energy loss.  Distance traversed by ions.  Longitudinal straggling.  Lateral straggling. For ions at a range of energies. Density of the gas is also read in. This replaces any value for density already read into Garfield. The Garfield SRIM interface makes use of the fact...

The TRIMCAT Module Reads in files from TRIM Data read includes gas pressure, positions and thicknesses of layers and a table of ion energy against position(x, y, z) and EM energy loss. Perform Numerical Differentiation Uses a lagrangian method to differentiate energy vs position to give the total ionisation dE/dx. Calculate the splitting between EM and nuclear energy losses Use the differentiated values for total dE/dx and the values of EM dE/dx. Generate electron clusters along the track Generates clusters of electrons according to the ionisation distribution and drifts them using Monte-Carlo methods.

The Matlab Preamplifier Simulation

The Results (1): The SRIM Interface

The Results (2): The TRIMCAT Module

The Results (3): The effect of the PGAC

4. CURRENT STATE OF THE PROJECT AND FUTURE DEVELOPMENTS Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

The Engineering Designs  PGAC complete.  Mechanical design of Bragg nearing completion at Daresbury Laboratory.  Designs ready in stages throughout this year.  Electrical design done by Bob Hyde in workshop at York.  PGAC complete.  Mechanical design of Bragg nearing completion at Daresbury Laboratory.  Designs ready in stages throughout this year.  Electrical design done by Bob Hyde in workshop at York. Drawings courtesy of Jon Strachan, STFC Daresbury Laboratory, Cheshire.

The Prototype  Prototype PGAC constructed at York. Ready for testing with fission source at Manchester.  Prototype Bragg volume to be constructed over the coming months – needs to be outsourced.  Prototype PGAC constructed at York. Ready for testing with fission source at Manchester.  Prototype Bragg volume to be constructed over the coming months – needs to be outsourced. Drawings courtesy of Jon Strachan, STFC Daresbury Laboratory, Cheshire.

The Simulations SRIM/TRIM Garfield Bragg Simulation Garfield PGAC Simulation Matlab Preamplifier Simulation Post Processing Software  Geant 4 Efficiency simulation SRIM/TRIM Garfield Bragg Simulation Garfield PGAC Simulation Matlab Preamplifier Simulation Post Processing Software  Geant 4 Efficiency simulation

ANY QUESTIONS? Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments Bragg Curve Spectroscopy The York Bragg Detector – Bragg Volume – PGAC Simulations – Simulation Path – SRIM/TRIM – Garfield – Matlab – Results Current state of the project and Future developments

The Munich Comparison Preliminary!