operational aspects 2008 run iscool isolde workshop 17-19 nov 2008 erwin siesling

Operational aspects

2008 run

ISCOOL

Isolde workshop 17-19 Nov 2008

Erwin Siesling

Isolde workshop 08: ISCOOL OP aspects E. Siesling 2

Overview

ISCOOL: RFQ cooler and buncher at Isolde

• Hardware• Functionality, principle and specs• Technical issues 2007/2008• Results 2008 run• Shutdown consolidation• Summary


ISCOOL hardware

Inj. Triplet Ej. TripletRFQ tank

Instrum.60 kV


ISCOOL hardware


HRS

GPS

Located right after the HRS separator magnets

RFQ Cooler and buncher

ISCOOL hardware

Isolde facility


60keV HV platform & RF

ISCOOL hardware

Isolde facility


ISCOOL functionality

• RFQ: Confines the beam and reduces energy spread for better transmission and higher mass spectroscopy efficiency

• Bunch mode: Bunches the beam for background supression

Continuous mode & Bunch mode


Courtesy Dr. H. Franberg

ISCOOL principle

He buffer-gas:Interactions decelerate the particles to a few eV

RF power:4 transverse rods. Confines the beam

Mathieu equation 2

02

4

rm

Ueq

RF

RF

Electrodes:Potentials along the axis. 3 last and extraction plate can be pulsed

HV extraction voltage:60kV to extract and accelerate the beam out of the RFQ

RFQRF

Bunch mode


• Emittance:• Transmission:• Cooling time:• Space charge:• Pulse width:

ISCOOL specs

from 35π.mm.mrad to 2.2 π.mm.mrad

better than 70% for A>39

TOF <1ms, one passage enough to cool the beam

up to 1E8/s !

depends on space charge and cooling time


• The ISCOOL has been performing remarkably well during the 2008 run with only a few minor technical problems

• 2007/8 shutdown consolidation:- elements controllable from RFQ workingset & QP array - vacuum leaks fixed & interconnections improved- re-aligned

• 2008 operation issues:- Excessive use of He buffer gas- RF amplifier break down (due to abrupt HV switching)

ISCOOL tech issues


• Workingset for all elements

2007/8 consolidation

• QP arrays: Archive to save and reproduce settings for different targets and users



Vacuum leaks repaired & connections improved



Re-alignment:

?

Aligned with respect to the faraday-cups: displacement of the beam with regard to the scanners of hor -10mm, vert +30mm stayed

With beam..


2008 Operation issues

He

Buffergas pressure: ~1E-2 mbar 4HeEstimated: 10-2mbar l/s

But…

Helium ‘addiction’:

- Using 3x more

- Bottle needs changing ~6 weeks

- Filling-up Isolde gas-recuperation tanks faster

He buffergas


2008 Operation issues

RF amplifier & synthesizer

High Voltage sensitive:

- Break down due to abrupt HV switching

- Will be replaced this shutdown (+ spare)

60kV


ISCOOL 2008 results

• ISCOOL transmission• Beamline transmission• Bunch mode


Inj. Triplet Ej. TripletRFQ tank

Instrum.

ISCOOL online transmission

0102030405060708090

0 50 100 150 200 250

Mass

tran

smis

sion

effi

ency

[%]

Continous mode Pulsed mode Slits

0

20

40

60

80

100

0 50 100 150 200 250

Mass

Tran

smis

sion

effi

cien

cy [%

]

Surface ion source plasma ion source MiniMono

Courtesy Dr. H. Franberg

Sources Modes

ISCOOL transmission >70% for A>39:- In general between 70-80% for plasma targets, somewhat higher for surface ion sources. Depends on the emittance coming from the ion source

- In pulsed mode some higher losses related to the trapping time


Beamline transmission

HRS

GPS Merging switchyardlosses 50-70%

ISCOOL

~35π.mm.mrad

~2π.mm.mrad

Higher mass spectroscopy

efficiency

100% transmission

Beamline transmission:- low emittance beam after the cooler is easily tuned to the different experiments with a transmission efficiency of up to 100%


Bunch mode

ISCOOLin bunch mode

Collaps

HRS

Background suppression of factor ~1E4 by gating on the beam pulse

46K beam 1E5 ions/s after the cooler.Collection time 20 min, with 300ms bunching, 12us gate and 2mW laser power

Ernesto Mane: ‘First results using the ISCOOL-COLLAPS apparatus’


Bunch mode

ISCOOLin bunch mode

REXtrap

HRS

ISCOOL gated by trap timing

(10 units = 20us)

20uS

New 'tricks' for REX injection:

- Mass purification at REXtrap using RF excitation. - Direct pulsed injection into EBIS without use of the trap: The space-charge of the RFQ bunches is much higher than what can be achieved with the trap. Acceptance of EBIS would be large enough and it would increase beam intensity to the linac.

Anna Gustafsson: ‘The REX low-energy toolbox’


• 2008/9 shutdown consolidation:- vacuum controls (Julien de Freitas)

- new RF amplifier (Pascal Fernier)

- MCP re-installed?

2008/9 shutdown


• Reliable 2008 performance with very few issues- RF amplifier will be replaced + spare- Vacuum will be integrated in the Isolde controls

• ISCOOL transmission 70-80% depending on mass and ion source

• Easy tuning and beamline transmission improved to 100%

• Bunch mode working well with future potential:- background suppression- mass purification at REX TRAP- direct injection in to REX EBIS

• Details in the 2008 ISCOOL performance report by Dr. H. Franberg, Dr. Pierre Delahaye, et al.

• ISCOOL webpage: http://ab-div-op-iso-rfqcb.web.cern.ch/

Summary


• Special thanks to Hanna, Pierre and Tim • The Isolde OP-team, AB/OP-PSB-iso

AB/ATB, AB/VAC, AB/PO, AB/CO and Alexandre Dorsival (SC/RP) for making the ISCOOL 2008 run a success

Thanks

operational aspects 2008 run iscool isolde workshop 17-19 nov 2008 erwin siesling

Documents

iscool isolde workshop

iscool op aspects

iscool specs

iscool hardware slide

bunch mode iscool

overview iscool

iscool functionality

iscoolcollaps apparatus