Experimental tests of HIE-ISOLDE beam instrumentation
HIE-ISOLDE diagnostic boxesEsteban D. CanteroCERN BE-BI-PM
HIE-ISOLDE meeting for BE/BI28 March 2014The research leading to
these results has received funding from the European Commission
under theFP7-PEOPLE-2010-ITN project CATHI (Marie Curie Actions -
ITN).Grant agreement PITN-GA-2010-264330.
OUTLINEHIE-ISOLDE diagnostic system overview:Beam
parameters.Short and long diagnostic boxes.Instruments and
devices.Measurement procedures.Faraday cup.Slit scanner.Silicon
detector.Collimators.Stripping foils.Synchronisation of
instruments.Actuators.2HIE ISOLDE beam parameters
Bunch period ~10 nsFreqRF ~ 100 MHzProjectiles: He to U 2 < A
/ q < 4.50.3 < E/A < 10 MeV/u
RIBs (pps to few pA).Stable beam (1 pA to 1 nA).
Normal setup procedures usestable beams, and scale the
accelerating and transport stagesto the desired A/q.
Repetition rate: 2 to 100 Hz.Macro pulse length: 50 to 500
ms.Micro-bunches separated 9.87 ns.
time3Short and Long diagnostic boxesDue to tight space
constraints in the longitudinal direction, we had to implement two
designs for the DBs:Linac: Short DBs (6).HEBT: Long DBs (12).
The functionality and operation of the instruments is similar in
the SDBs and LDBs. The only difference between them is that the
SDBs have a compact Faraday cup.
Depending on which devices are included on each DB, there can be
up to 4 different types/configurations of DBs.
scanning slitstripping foilsFCSi. detcollimatorsvacuum
portbeam
short FClong FC4Instruments and
devicesInstrumentQtyInputsOutputsPlane *PositionsConnected
toFaraday cup18V repellerI signal plate2IN OUTFC preamplifier +VME
boardScanning slit181continuous stroke 135 mmSi detector2HVparticle
energy and time of arrival2IN OUTand continuous
adjustmentpreamplifier + VME-NIM modulesCollimators 11214
setpointsand continuous adjustmentCollimators 2614 setpointsand
continuous adjustmentStripping foils613 setpointsand continuous
adjustment* to avoid collisions, only one device at a time can be
inserted on each plane of the DB.5Measurements procedures Beam
intensity: Faraday cup (+ collimators).Used every day for setting
up the accelerator and aligning and transporting the beam.Beam
transverse profiles (and position): Scanning slit + FC.Horizontal
and vertical profiles.Expected ~1000 scans per year for each
box.Beam longitudinal profile: Silicon detectors.Energy and time
spectra.To obtain the time of flight, the spectra with the arrival
time to both detectors needs to be combined (measurements might
take place in parallel if we use an annular Si detector).Energy
spectra might be acquired during the cavities phasing
(daily/weekly). TOF spectra will be used to provide a calibration
point for E/A of the bending magnet (~twice a year).Transverse
emittance: 2 scanning slits + FC (or REX slit + grid
emittancemeter).Once a year.Beam cleaning: collimators or stripping
foils.
6Faraday cupA negative bias voltage is applied to a repeller
cylinder in order to avoid the escape of secondary
electrons.Current amplification and readout is implemented with a
preamplifier + VME board.Repeller voltage and integration time can
be modified by an expert user.Requires the time signal for the EBIS
pulse in order to trigger the charge collection loop.
plate-Vrep Z+qVrep ~ -60 VIsignal plate (average) ~ from 0.1 pA
to 1 nA.77Scanning slitA blade with a V-shaped slit is scanned
upstream the FC.Vertical and horizontal profiles are acquired, and
the beam position is calculated from them.A 1 mm collimator hole is
also included in the blade and can be used for beam alignment. The
position of the blade needs to be controlled for the full stroke
(135 mm). The actuator is driven by a stepper motor.
DetectorBeam
88Silicon detector
preamplifiercharged particles spectroscopytime of flightenergy
chaintiming chainTotal particle energyMass compositionParticle
speedBunch length
energy spectrumTOF spectrumDetector bias (60 or 100 V) supplied
through the preamplifier.Preamplifier power: 24 V, 12 V provided by
shaper amplifier.Leakage current monitoring can be used to
determine detector aging and also to block the beam if dose rate is
too high.Requires the time signal for the RF master-oscillator and
the EBIS pulse for triggering the TDC and gating the
acquisition.Integration time controlled by the user.Works at an
average rate of ~100s particles per second. Beam intensity needs to
be severely reduced placing collimating foils in DB2 and DB3.
99Silicon detector IICurrent implementation:
Alternative solution (under evaluation):Si. detector +
preamplifier + fast ADC (CAEN) + digital processing of
signal(outputs peak height + timestamp)(ADC outputs peak height,
TDC outputs timestamp)From peak height and timestamps, energy and
timing spectra are generated.Gating with the EBIS pulse and leakage
current monitoring is not yet implemented.1010Collimators and
stripping foilsPreset positions (1 to 4, or OUT) or arbitrary
value.Actuator driven by a stepper motor.
1111Synchronisation of instrumentsFaraday cup preamplifier
charge collection:Triggered by the EBIS pulse.Beam transverse
profiles:Scan blade position while acquiring beamlet current with
the FC.Transverse emittance:Scan position of two blades while
acquiring beamlet current with the FC.Si detector
acquisition:Triggered by the EBIS pulse.Time of flight
measurements:If the first Si detector is annular, beam can arrive
to both detectors at the same time.The RF masterclock pulse is used
as a time reference.
1212Actuators reviewFaraday cup and Si detector:Stepper motor
POWERMAX II, P21NRXD-LNF-NS-00.Limit switches, only IN OUT position
needed.Collimators and stripping foils:Same stepper motor as
detectors.Intermediate actuator positions are needed.Scanning
slit:Stepper motor Ametek HY200 2226 0160.Limit switches, accurate
positioning (