“X-ray background in Miniball”

Elisa RapisardaInstituut voor Kern- en Stralingsfysica, K.U.Leuven

for the MINIBALL, REX- and HIE-ISOLDE collaboration(Work of the Summer Student Jean Baptiste Durrive)

Position in the hall

Present Shielding

Note technique CERN-SC-2007-073-RP-TN EDMS No. 880127 v.1 Consolidation du blindage des cavités accélératrices « IH-structure » et « 9-gaps resonator » de REX-ISOLDE A. Dorsival

The three spectra below show the background without any concrete shielding (after the orange mobile lead shield was removed), with two layers of concrete and with the full shielding. It looks as though the detectors are still seeing quite a lot of Bremsstrahlung. We suspect much of this comes from the place where the beam line exits the 9-gap resonator, which is not really shielded by this concrete wall."

2006

Energy (keV)

The actual background level in MINIBALL is “acceptable”

We would like to reduce it as low as possible No random particle-gamma coincidences will be ideal !!!! a factor 10 lower than the current level of the background

PresentlyC

ount

s (a

.u.)

Experimental γ-particle coincidence spectrum, background (random coincidence) subtracted

Simulated GEANT 4

2+0+ 104Pd

2+0+ 200Po

New measurements of Background

Determination of X-ray spectrum due to the LINAC is possible thanks to the DAQ synchronized with the EBIS pulse (In-Beam and OFF-beam background are acquired)

Relative measurements and comparison possible

AIM: Measurement of the absolute background in Miniball

were performed in June

• varying the 9GAP power from 0kW to 85kW when LINAC ON and OFF• Varying the 9GAP power from 0kW to 85 kW when beam in the LINAC• With/without the 3 Pb layers, 1cm thick

HARD: normalization to the Miniball solid

angle

Estimation of Miniball efficiency (well know when source in target position)

MORE: Single Crystal, stand aloneHpGe from radioprotection

group also used

IN Beam window (1ms)OFF Beam window (1ms)

511 keV

Per 1000 EBIS pulses

No Shielding, 84 kW in 9 GAP

IN Beam minus OFF Beam

End Point 300 keV (Applied Voltage in 9GAP 400V Friderick)

No Lead Panel ShieldingPer 1000 EBIS pulses

84 kW

70 kW

55 kW

25 kW

Lead Shielding .vs. no Lead Shielding

Without Shielding With Shielding(three Pb panel 1cm thick each)

84 kW in 9 GAP, 1000 EBIS pulses

X-rays Intensity .vs. 9GAP power

continuum

Unfolding I …NOTE: We need to subtract the Compton

NOTE: The experimental spectrum must be unfolded by the

efficiency of Miniball

Miniball energy threshold around 40-60 keV depending on the cluster

84 kW in 9 GAP, with shielding

Unfolding II…

GEANT4 simulationSource: 9GAP

Experimentally measuredSource: Miniball target

Assuming an approximate value ofε≈ 0.0015 %

X-ray yields ≈ 107 per 1000 EBIS pulse per 4π

Detector thresholds not included in the simulation

END

Present

11/2014

4/2016

3/2017

3 MeV/u

5.5 MeV/u

10 MeV/u

10 MeV/u

HIE-Linac Installation

5.5 MeV/u

• 3 experimental stations (2 installed in stage1)

• TSR line and optional ‘car park’ line• Modular lattice• 8 lines: XL (REX Linac), XT00 –

XT06 (REX Transfer)

10 MeV/u

15 MeV/u

LINAC

The plot shows the hCoreSumIB spectrum (sum of all cores, calibrated in keV and gated on the in-beam window) minus the hCoreSumOB (the equivalent for off-beam).

2010 IN beam = EBISOFF beam = no EBIS

extra shielding around the beam line where it emerges from the bunker. extra shielding inside the bunker: on the front face (side nearest to Miniball) Extra shielding between the 9-gap and the magnetic quadrupole BEN.MQ30

Sum

of a

ll C

ores

Energy (keV)

HIE-ISOLDE: three objectives

• REX energy upgrade and increase of current capacityEnergy upgrade in three stages: 5.5 MeV/u and 10 MeV/u and lower energy capacityREX trap and breeder upgrade

• ISOLDE proton driver beam intensity upgrade 2 to 6 mA (linac 4)Faster cycling of the boosterNew target stations for ISOLDE

• ISOLDE radioactive ion beam quality improvementSmaller longitudinal and transverse emittanceHigher charge state for selected usersBetter mass resolutionTarget and ion source development e.g. RILIS