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Lyon 2005 DIPAC Lyon 2005 7 th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Instrumentation in small, low energy machines Ulrich Raich CERN AB-BDI.

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Presentation on theme: "Lyon 2005 DIPAC Lyon 2005 7 th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Instrumentation in small, low energy machines Ulrich Raich CERN AB-BDI."— Presentation transcript:

1 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Instrumentation in small, low energy machines Ulrich Raich CERN AB-BDI

2 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI The LHC The LHC is CERNs flagship project but … it is not exactly a small, low energy machine! why start with the LHC? Dump line Proton source Proton Linac Ion Linac RFQ Duo Plasmatron Proton source Cyclotron resonance Ion source

3 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Luminosity Quality factor of a collider: luminosity Depends on k b : number of bunches N: number of particles per bunch ε n : emittance LEP was limited in energy by synchroton radiation In LEP, due to Landau damping, the biggest machine was largely responsible for beam quality. In LHC the injectors determine beam quality

4 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Peculiarities of small machines Particles have small magnetic rigidity Bρ Particles are easy to bend Beam spot and angles are large (adiabatic damping) physical emittance shrinks factor 1500 from 50MeV – 450 GeV They need tight mesh of focusing magnets (leaves little space for instrumentation) Space charge Energy deposition in intercepting matter is high Few instruments but large variety Particle speed changes with acceleration Photo GSI Darmstatt

5 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Uses of small machines Small machines: –Injectors for bigger machines –Test stands –Medical machines –Accelerators for industrial use (ion implantation, material tests) even the Louvre has an accelerator –Accelerators at Universities or small research institutes

6 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Intensity measurements Faraday Cup Electrode: 1 mm stainless steel Only low energy particles can be measured Very low intensities (down to 1 pA) can be measured Creation of secondary electrons of low energy (below 20 eV) Repelling electrode with some 100 V polarisation voltage pushes secondary electrons back onto the electrode Contributed by G. Molinari and V. Prieto

7 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Repelling secondary electrons With increasing repelling voltage the electrons do not escape the Faraday Cup any more and the current measured stays stable. At 40V and above no decrease in the Cup current is observed any more

8 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Measurements of ion charge-state distribution Faraday Cup slit Spectrometer magnets

9 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Current transformers Often very close to pulsing magnetic elements Needs good shielding Long beam pulses from ion sources (typical 100μs) Digitization of raw signal with digital integration is possible

10 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Magnetic shielding Shield should extend along the vacuum chamber length > diameter of opening Shield should be symmetrical to the beam axis Air gaps must be avoided especially along the beam axis Shield should have highest μ possible but should not saturate monitor Soft iron (μ1) Transformer steel (μ2) Permalloy (μ3)

11 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Calibration of AC current transformers The transformer is calibrated with a very precise current source The calibration signal is injected into a separate calibration winding A calibration procedure executed before the running period A calibration pulse before the beam pulse measured with the beam signal Trace contributed by F. Lenardon

12 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI with the following constants: NA: Avogadros number m e and r e : electron rest mass and classical electron radius c: speed of light the following target material properties: ρ: material density A T and Z T : the atomic mass and nuclear charge and the particle properties: Z p : particle charge β: the particles velocity and Dependance on Interaction of particles with intercepting matter

13 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Screen Tests Penetration depth of ions at 4 MeV/u: <10µm Particle energy is deposited in very small volume Heat load and electric charging becomes a problem Several screen materials tested T. Lefevre, this conference

14 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Test for resistance against heat-shock Material g/cm 3 c p at 20ºC J/gK k at 100ºC W/mK T max ºC R at 400 ºC.cm Al 2 O ZrO BN Better for electrical conductivity (>400 ºC ) Better for thermal properties (higher conductivity, higher heat capacity) Use as reference question

15 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Wire Scanners A thin wire is quickly moved across the beam Secondary particle shower is detected outside the vacuum chamber on a scintillator/photo-multiplier assembly Position and photo-multiplier signal are recorded simultaneously

16 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Problems at low energy Secondary particle shower intensity in dependence of primary beam energy

17 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Wire scanners and partially stripped ions Partially stripped ions loose electrons when interacting with the wire The beam is lost Can measure amplitude distribution however

18 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Transforming angular distribution to profile A slit produces a vertical slice in transverse phase space Moving the slit scans the phase space When moving through a drift space the angles dont change (horizontal move in phase space) When moving through a quadrupole the position does not change but the angle does (vertical move in phase space) x x slit Influence of a quadrupole slit x x x x Influence of a drift space slit

19 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI The Slit Method 3d plot from P. Forck

20 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Single pulse emittance measurement Kickers slit SEMgrid Every 100 ns a new profile

21 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Result of single pulse emittance measurement

22 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Multi-slit measurement Needs high resolution profile detector Must make sure that profiles dont overlap beam Scintillator + TV + frame grabber often used as profile detector Very old idea, was used with photographic plates

23 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Pepperpot Uses small holes instead of slits Measures horizontal and vertical emittance in a single shot Photo P. Forck

24 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI Longitudinal emittance E φ Spectrometer magnet kicker slit buncher Spectrometer magnet kicker SEMgrid Spectrometer transforms energies into positions Buncher transforms time into Energy

25 Lyon 2005 DIPAC Lyon th DIPAC Lyon June 2005Ulrich Raich CERN AB/BDI The End Thanks for your attention


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