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CANREB Nier spectrometer
Document Type:
Requirements Specification
Release:
1
Author(s):
Ames
Release Date
Name:
Author:
Friedhelm Ames
Reviewed By:
Suresh
Saminathan
Approved By:
Reiner Kruecken
2013/05/11
Signature:
Date:
Note: Before using a copy (electronic or printed) of this document you must ensure
that your copy is identical to the released document, which is stored on TRIUMF’s
document server.
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CANREB Nier spectrometer
Release No. 1
Release Date.: 2013/05/11
History of Changes
Release
Number
1
Date
2013-05-11
Description of Changes
First release of draft document
Author(s)
F. Ames
Product Overview
The CANREB Nier spectrometer should separate the ions extracted from the CANREB EBIS
according to their mass to charge ratio. A Nier or Mattauch Herzog spectrometer consist of an
electrostatic and a magnetic beander, which allows separation of ions according to their mass to
charge ratio and Part of the beam line in front of the EBIS will be used by both the injected ions
and the extracted ion pulses. The energy of the ions has to be adapted to the acceptance of the
accelerator system and will depend on the mass to charge ratio of the desired ion beam. Figure 1
shows a schematic of the beam line elements in between the CANREB beam buncher and the
EBIS. A Nier spectrometer consists of an electrostatic and a magnetic dipole element. This
allows an achromatic mode of operation resulting in a high mass resolving power even with a
beam with a high energy spread like it is expected from an EBIS. In our case it contains
additional focusing elements in between the dipoles. The exit of the Nier spectrometer will
connect to the beam line leading to the accelerator. The boxes in blue will be part of the Nier
spectrometer deliverable.
This document covers only the basic general specifications of the Nier spectrometer. It only
includes basic functions of the individual devices The detailed specifications for those will be
based on this and will have to be defined after the layout has been finished.
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CANREB Nier spectrometer
Release No. 1
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Figure 1: Block diagram of the EBIS and CANREB components up-and-downstream thereof.
2. Requirements
In the following the requirements of the CANREB Nier spectrometer system are given.
1.1
General requirement
RS 1
The Nier spectrometer will be installed at the ground level of the ARIEL building.
The layout has to fit into the constrains of the building. The exit of the beam has to
connect into the beam line to the accelerator and the beam line should not interfere with
the singly charge ion beam line from ISAC.
Rationale:
The Nier spectrometer has to fit into the overall design.
RS 2
The beam line leading into the EBIS shall provide the possibility for differential
pumping. Direct sight between the EBIS and the buncher should be avoided.
Rationale:
This is necessary to maintain the differences in operating pressures of the
different components. The vacuum pressure inside the EBIS will be 10-12 mbar. The
pressure inside the buncher will be 10-2 mbar. The beam lines of the spectrometer will
be at an intermediate level (see RS 5).
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CANREB Nier spectrometer
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Release Date.: 2013/05/11
RS 3
The energy of the highly charged ions will be up to 14 qkeV. It will be a pulsed
beam structure with a pulse repetition frequency of 100 Hz. The pulse length of the singly
charged ions to be injected into the EBIS will be 1 µs and the pulse length of the highly
charged ions coming out of the EBIS will be up to 1 ms. The total current will not exceed
several µA.
Phase space parameters of the beam should match those given by the acceptance and
emittance of the EBIS. (see EBIS requirements specifications: The transverse emittance
at 14 qkeV will be less than 20 µm and the energy spread less than 100 qeV)
Rationale:
Beam parameters are defined by the buncher, EBIS and accelerator.
RS 4
The mass resolution of the separator for a beam defined in RS 3 should be M/ΔM
>200, with ΔM including 90% of the beam intensity of all ions with one mass to charge
ratio. The spectrometer should cover a mass range up to A/q =50.
Rationale: This resolution will allow the separation of the desired ions from background
ions from the residual gas in the EBIS or molecular contaminations in the singly
charged incoming beam. Although the normal operation mode is at a mass to charge
ratio below 7, the higher range allows for measuring charge state distributions both of
the desired ion beam and residual gas ions. This is necessary to set up the EBIS and
determine optimum running parameters.
RS 5
The vacuum in the separator has to be below 4 · 10-8 Torr.
Rationale:
This will allow the transport of highly charged ions. The beam loss over
10 m at his vacuum level due to charge exchange will be 6.5% for U35+ or 3.5% for
Rb15+.
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CANREB Nier spectrometer
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RS 6
Ion optical elements in the section between the EBIS and the first electrostatic
bender have to be switchable between injection and extraction mode. The frequency of
the switching will be up to 100 Hz. The pulse duration for the 2 modes will be
determined by the pulse length of the injected beam (typically 1 µs), the pulse duration of
the extracted beam (up to 1 ms) and the breeding time in the EBIS. The rise and fall times
for the voltages at the electrostatic elements have to be optimized in order to minimize
dead time of the system.
Rationale:
The EBIS will operate in a pulsed mode. In order to achieve maximum
efficiency the ion optical elements have to be changed to match the beam for injection
and extraction. During the rise and fall times of the voltages the ion optics matches
neither one of the two modes and cannot be used.
RS 7
The set up should include a sufficient number of beam diagnostics elements to
determine position and size of the beam as well as transmission throughout the system.
The exact number has to be specified, after the layout and number of beam optics
elements has been defined. Diagnostic elements will include Faraday cups, beam profile
monitors, low intensity monitors and an emittance meter. All diagnostic elements have to
be designed to handle the pulsed beams going in or coming out of the EBIS. The intensity
range to be covered will range from several ions per second to average currents up to 1
µA. Diagnostic elements will include Faraday cups, beam profile monitors, low intensity
monitors and an emittance meter.
Rationale:
The type of diagnostic elements is based on experiments with similar
systems.
Comment:
The exact number has to be specified, after the layout and number of
beam optics elements has been defined.
RS 8
Wherever possible ion optical and beam line elements shall use the same designs,
which are used for similar elements within the CANREB project.
Rationale:
This will ensure maximum synergy within the project and ease of
operation.
RS 9
All devices shall be controlled via the standard TRIUMF control system EPICS.
Rationale:
The Nier spectrometer will be part of the ISAC/ARIEL beam delivery.
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