CATHI and the HIE-ISOLDE Design Study

Richard CatherallISOLDE Technical Coordinator

ISOLDE Users Workshop15th – 17th December 2014

CATHI:Cryogenics, Accelerators and Targets for HIE-ISOLDE

HIE-ISOLDE PROJECT

High Energy

Upgrade

Design Study

CATHI

• A European funded Initial Training Network Program• 20 Marie Curie Fellows• A project within a project• Design Study

– Address the issues associated with an increase in p-beam intensity and energy– Investigate upgrades for an improvement in beam quality

Who was doing what?Marie Curie Fellow

Michal Czapski Pol Target material developments

Mathieu Augustin Fra HRS layout and magnet design, Off-line 2

Carla Babcock Can RFQ Cooler

Jacobo Montano Ven Target and Frontend Developments. Off-line 2

Serena Cimmino Ita Target design

Mario Hermann Ger Vacuum: RFQ Cooler, Dry pumps, Fast gate valves

Andrea Polato Ita Ventilation

Andrej Shornikov (ER) Rus EBIS upgrade

Leonel Morejon Cub Fluka Calculations

Martino Colciago Ita HRS Magnet controls

Martin Breitenfeld Ger HRS magnet design and MRTOF

Maddalena Maietta Ita Radioisotope propagation

Roger Barlow Eng HT modulator

Valentina Venturi Ita Beam dumps

Outline• Infrastructure

– Baseline Parameters– Beam dumps– Shielding– Vacuum– Ventilation

• Targets and FE– Target materials– Target design– Frontend– Off-line separator

• Beam quality– New RFQ Cooler– MR-TOF for ISOLDE– HRS Separator

• Magnet Design and layout

– EBIS electron gun

Base line parameters

• Linac 4– Linac 4 will be able to provide 5 x 1013 ppp = 1.25

x 1013/ring• Based on 40mA from the ion source

– Could possibly go beyond this value with a combination of different options

• Increase in source current output• An increase in pulse length• Chopping factor

– All need to be in place for testing

Protons/pulse Intensity(µA)

Energy(GeV)

Cycle(s)

Power(kW)

3.3x1013 2.2 1.4 1.2 3.1

1x1014 6.7 1.4 1.2 9.3

1x1014 6.7 2.0 1.2 13.3

Protons/pulse Intensity(µA)

Energy(GeV)

Cycle(s)

Power(kW)

5.0x1013 3.33 1.4 1.2 4.67

6.4x1013 4.3 1.4 1.2 6.0

1x1014 6.7 2.0 1.2 13.3

• Booster RF upgrade– CO2/CO4 upgrade would limit

protons to 1.4 x 1013/ring• Could be increased with a power

amplifier upgrade after LS2– Finemet upgrade (+MOSFET

amplifiers) = 2.5x1013/ring• Depends on the upgrade solution

chosen

Beam dumps

• Estimations made for different heat transfer coefficients• New design based on PSB design

Valentina Venturi

Shielding and activation

• Simulations and Design of further shielding

• Simulations for the implementation of extended target storage within the same building

Figure 5 : Views from the target storage geometry. Top 2D (left) and top 3D (right).

Figure 9 : Dose in µSv/h on target storage and surrounding areas. 108 stored targets situated in shelves next to opposite walls inside the storage as shown. View from top.

Leonel Morejon

Dry-pump stand and test

Substitution of normal, oil sealed pumps with dry pumps and pre-filtering before storage

Selective filtering between primary pump and dummy gas storage

Spectroscopy on filters in progress

M. Hermann, G. Vandoni

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VentilationPurpose of the airlocks:• Create a volume between Tunnel and Class A Laboratory in such a way to:

– Avoid activated air backflows from the Tunnel to the Class A Laboratory;– Prevent the Class A Laboratory evacuation in case of Tunnel ventilation stop (and vice versa);– Enhance a more flexible pressure regulation in the two buildings;

• Increase the leaktightness of the structure• Ventilation separation in progress

NOT FEASABLE

Andrea Polato

Progress on Infrastructure

• Supplementary shielding has already been installed…mainly to reduce radiation levels in neighbouring MEDICIS lab.

• Validation and implementation of extra storage will eliminate the need for unnecessary transport in the long term.

• Ventilation modifications are already in progress and will contribute to a reduction in activated air release as from next year.

• Still awaiting results on spectroscopy of filters from the dry pump tests.

• Beam dumps are a critical item for any increase in intensity and energy and should be upgraded during LS2 – 2018-2019.

Outline• Infrastructure

– Baseline Parameters– Beam dumps– Shielding– Vacuum– Ventilation

• Targets and FE– Target materials– Target design– Frontend– Off-line separator

• Beam quality– New RFQ Cooler– MR-TOF for ISOLDE– HRS Separator

• Magnet Design and layout

– EBIS electron gun

Study of prototype refractory ceramics (SiC and Al 2O3 ) with open unidirectional porosity

Michal Czapski

Uncouple container and heating functions

Ta container

Graphite heater

Graphite insulation

Graphite rigid connectors

Graphite flexible connectors

• Utilization of graphite pieces• Reduction of Tantalum weight 50%=> nuclear waste reduction

Serena Cimmino

Prototype

Thermocouple

• Insertion of a thermocouple between the heater and the container

=> Direct Temperature measurement (without calibration)

Serena Cimmino

Two stage extraction

For determining the optimum intermediate electrode configuration:• Thermal tests and simulations with ion

source @2000°C• HV insulation tests up to 5kV with

respect the ion source• Extraction efficiency measurements• Ionized air conductivity measurements• Acceleration gap pressure measurements

60 kV57 kVGround

Few geometrical parameters are studied in order to find an optimum electrode design:• Aperture• Acceleration gap• Tip shape

Jacobo Montano

Two stage extractionThermal characterization

Jacobo Montano

Charge pump modulator3. A new modulator concept

Advantages

• Modulation recovery time adjustable

• Requires a single low current high precision power supply (High power supply not necessary)

• A single HV switch is required (compared to C modulator which uses 3)

1) In this circuit a 400 nF buffer capacitor (C1) and the target capacitance (C2) are charged to 60 kV by a low power, high precision d.c. power supply (HVPS)

2) Immediately prior to beam impact the HVPS is disconnected from the target and the buffer capacitor using a 90 kV rated semiconductor switch (HV_Switch1). During beam impact the target capacitance is rapidly discharged to 54 kV. Then the buffer capacitor begins to re-establish voltage on the target to 99,4% of its initial value.

3) After 1 ms a feedback loop controlling an auxiliary high voltage amplifier is switch on and increases the buffer capacitor potential. This additional voltage brings the target voltage back to the required +/- 0.6 V tolerance within 5 ms.

4) Finally, when the target has recovered to a sufficient high impedance, the feedback loop is opened and the HVPS is re-connected to the target to maintain the stable 60 kV voltage.

Roger Barlow

Charge pump modulatorAssembly / Tank housing

• Custom built tank enclosure

• Tank is filled with dielectric oil

• Has a second ‘skin’ for oil leak protection

• Contains the modulator system, buffer capacitor bank, HV precision divider, static and dynamic load

Tank housingCapacitor bank0.05uF 75kVdc (hivoltcapacitors)

75kVdc high precision dividerVD75-20Y-BDSC-KC-BEA/PB/F (RossEngineering)

Viewing window

Essex HV connector

Oil temp gauge

Pressure sensor Oil filter

Filler cap

EAPPC2014: A charge-pump 60kV modulator for the ISOLDE target extraction voltage , R. A. Barlow1, B. Bleus1, A. Fowler*1, H. Gaudillet1, T. Gharsa1, J. Schipper1

1800mm

Roger Barlow

Off-Line separator 2

• Built and operated in B.275 earlier this year• Now being moved to B.3• To be used for FE modification tests, beam optics for RFQ Cooler, new

magnet design tests…• Can also be used for target production/prototype testing

M. Augustin, J. Montano

Progress on target and FE• Post-irradiation analyses is required of the remaining irradiated

samples• Graphite heat shields need to be tested further but show promising

results already– Step in the right direction uniform heat distribution and for waste

treatment• Further testing required for the two-stage extraction

– However any modifications incur:• Modifications of the FE’s (LS2 during their replacement?)• Amendments to the target production contract• Modifications to OL separators and production protocol

• HT modulator design looks promising. Implementation could be in 2016/2017– Note that new HT power supplies (compatible with the modulator design)

will be delivered in October 2015

Outline• Infrastructure

– Baseline Parameters– Beam dumps– Shielding– Vacuum– Ventilation

• Targets and FE– Target materials– Target design– Frontend– Off-line separator

• Beam quality– New RFQ Cooler– MR-TOF for ISOLDE– HRS Separator

• Magnet Design and layout

– EBIS electron gun

RFQ Cooler1. Alignment

– Internal and external alignment possibilities and done externally

2. Pressure monitoring– Possibility to measure gas pressure inside

the electrodes– Modification of conductance

3. Mechanical and electrical design– Investigating mechanical support to

maintain electrodes in place– Improved wiring and insulation to avoid

short-circuits

4. Laser pumping1. Modification of apertures to allow lasers

to interact with ions in the bunched region

Carla Babcock

MR-TOF for ISOLDE

Can it replace a magnetic separator? • Surely not with state of the art, too small

current: • 1000 ions per cycle (~4ms for

RFWHM=20000) • 3e5 ions per 1.2s, but usually a huge

fraction is contamination!

But the performance could be improved: • Higher energy inside the MR-ToF • Bigger device to reduce density • Investigations are still ongoing to improve

throughput

Ion-beam composition analysis • direct feedback for target/line

optimization • sampling of release curve possible • single ion sensitivity to detect

lowest yields • no upper limit on half-life as with

decay station • not hindered by decay branching

ratio

Martin Breitenfeld

HRS Separator LayoutBeam emittance ε=3π.mm.mrad R = 20 000for more than 99% transmission of pure beam R ~ 23 000 for 90% transmission of pure beam

Mathieu Augustin

New Magnet Design

Schematic view in cross section of the new HRS magnet (H-type), and partial view in 3D, featuring the pole face windings technology (picture credit to M. Breitenfeldt)

• H type magnet, mechanically more stable, possibility of better pole face machining • Yoke made of laminated steel reduction of eddy currents, allowing an increase in cycling

speed (~1min VS 15min) • Poleface windings allow the adjustment of the magnetic field along the beam axis.

Martin Breitenfeld, Mathieu Augustin

Beam Quality Summary• The new RFQ Cooler is (almost) built

– To be coupled to the Off-Line 2 for testing and characterization with beam• MR-TOF is a promising tool for both experiments requiring high

resolution and target characterization– Already discussed in the ISCC but WG required to further pursue design

and integration• Could well be an out-of-beam device

• HRS: A long way from being implemented– New magnet design looks very promising– Would like to see a 90 deg “compact version” built and tested on Off-line

2 as a pre-requisite to any further decisions• REXEBIS developments should be strongly encouraged

– For HIE-ISOLDE and for possibly the TSR.

CATHI Final Review

• Held on 22nd to 26th September in Barcelona• Wrap-up of all the HIE-ISOLDE – CATHI activities• https://indico.cern.ch/event/316392/page/5• The CATHI Fellows have made excellent

contributions to the HIE-ISOLDE project• They will be missed!

Spare Slides

Target simulations• The use of borated polyethelyne to reduce activation

Figure 11 : Views 3D of the target wrapped ina borated polyethylene box of 10-30 cm thickness.

|Table 1 : Values of activity of the air for the cases when the target is at GPS and when it is at HRS. Wrapped and Unwrapped stand for the case when the target is not covered by the polyethylene and when it is respectively. The values are normalized to a proton (ppp: per primary particle)

• The research leading to these results has received funding from the European Commission under the FP7-PEOPLE-2010-ITN project CATHI (Marie Curie Actions - ITN). Grant agreement no PITN-GA-2010-264330.

On-line Sampling :• Realized along the primary pumping system, with active carbon and

cellulose filters installed downstream of the turbomolecular pumps;

• Spectroscopy Analysis.

Use of a tape station to• analyze ACTIVITY and evaluate the TIME OF

FLIGHT of different gas species (spectroscopy);

• TEST the accuracy of Monte Carlo model (time dependent mode).

Sampling and measurement of radioactive species

Maddalena Maietta M. Hermann, G. Vandoni

Cold Line Study…

• Additional 4th cooled finger assembled by EB welding

• Cooled line screwed on it• Thermal contact by pressure

Actual design Proposed design

=> This solution has still to be tested and validated by a prototype

Serena Cimmino

Two stage extractionExtraction optics

Particle tracking (second gap)

The low energy first extraction produces large beams. The second gap focalizes the beam

Jacobo Montano

3. Charge pump modulatorHardware assembly

• C modulator topology / Charge pump topology (Reconfigurable prototype)

• Design can support up to 3 (90kV) Belkhe switches

• Structure all Vetronite • Static charge for ‘on-board’ testing• Compact design

HV supplies/Amplifier

Signal feedtroughs

HV switch

Diode

Hall effect

CTStatic charge

Roger Barlow

ISOLDE Beam DumpsOption 2

• Replace existing beam dumps• Advantages

– Low dose rate for installation– Take advantage to improve shielding (see next slides)– Reduction in air activation through new design

• Disadvantages– Removal, storage and replacement of ~3500m3 of earth,

about half of which is activated.– Handling and storage of radioactive beam dump– Still require cooling and its associated disadvantages

ISOLDE Beam Dumps Option 1

• Insert a PSB like water-cooled beam dump in front of existing beam dumps.– Advantages:

• Cheaper option• Based on known design• “easier” access

– Disadvantages• Implementation and maintenance of a cooling system

– Activated water

• Contribution to target area air activation and consequent release to atmosphere.

• High dose rate for installation

Shielding

• Further shielding required to attenuate dose rates observed during operation and under certain conditions:– 2uA of p-beam on thick ISOLDE targets (>50gcm-2)– Identified by RP in https://edms.cern.ch/document/1142606/1

CERN-DGS-2010-006-RP-SN– Impact of p-beam intensity and energy increase on radiation

dose rates outside the CERN perimeter to be assessed• Can be combined with an upgrade of the ISOLDE beam

dumps• Requires major excavation work of activated earth

Shielding

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REX-EBIS: Electron Beam Ion Source for HIE-ISOLDE

Design values for EBIS (HIE-ISOLDE/TSR@ISOLDE application ) / available now with REXEBIS

Electron energy [kV] 150 / 5

Electron current [A] 2-5 / 0.2

Electron current density [A/cm2] 1-2x104 / 100

New EBIS – High Energy Compression and Current (HEC2) EBIS

Main challenge – produce the high compression electron beam

Goal – have a reliable design of the HEC2 electron gun on earliest possible stage

Priorities and the goal setting

Realization – in a joint effort with BNL, based on BNL design and infrastructure (BNL Test-EBIS), funded and manned by CERN

See presentation by A. Shornikov