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 (