2. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 1/16 New WS design - Brain storm session

3. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 2/16 Introduction First rotational WS in SPS in 1973. Later WS in PS, LEP, PSB and finally in LHC. LHCSPSPSPSB TypeLinearLinear (DESY) Rotating Speed [m/s]20.4 - 1610 - 20 Servo typePosition Speed Servo devicePotentio- meter Tachometer Position read- out device Potentio- meter Optical Ruler Potentio- meter Resolver Amplitude read- out dev. Scint./ PMT Scint./ PMT Scint./ PMT Scint./PMT & SEM

4. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 3/16 Encountered problems Breaking wires due to: –Beam interaction. –Induced RF power. Instabilities of position and profile measurements due to: –Inaccuracy of position measurements. –Flexibility, vibrations in mechanics and wire (in some cases). Aging bellows in PS (broke after ~13000 scans). Outgassing bellows in LHC during bake-out. Timing jitter in PS. Magnet quenching in LHC (simulations GEANT4). Fixation wires in fork. Wire drift into beam due to offset in speed feedback loop (PS).

5. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 4/16 Different WS types

6. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 5/16 Profile examples LHC beam, σ = 1mm LHC beam, σ = 320µm

7. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 6/16 Graphs Federico: (every point in the graphs is the result of 500 fit calculations.) –1. Systematic error on beam size due to position resolution limitation. –2. Statistical error on beam size due to limitation in number of primary events. –3. Statistical error on beam size due to presence of noise on amplitude measurement. –4. Statistical error on beam size due to presence of noise on position measurement. 2 13 4 © F.Roncarolo

8. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 7/16 PMT signal LHC quantityunitsaccum. q.units pilot bunch intensity (σ y =250μm @ 450GeV)5.00E+09p p center portion interacting with wire (d=30μm)4% 2.00E+08p interaction/detection efficiency (GEANT)2.50E-05 5.00E+03p average energy deposition (GEANT)10MeV/p5.00E+04MeV BC408 scintillator conversion efficiency8.00E+03photons/MeV4.00E+08ph transmission efficiency scintillator to PMT10%4.00E+07ph quantum efficiency S20 photocathode PMT20%electrons/photon8.00E+06el gain 6-stage XP2243B PMT1.00E+04 8.00E+10el output charge PMT1.60E-19C/el1.28E-08C RMS bunch length @ 450GeV (l=11.12 cm)3.75E-10s PMT pulse duration FWHM (~scintillator p.d.)2.60E-9s theoretical output current PMT FWHM 4.92E+00A

9. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 8/16 Thermionic Em. Current 1 st Batch Injection 2 nd Batch Injection Beam Energy Ramp Voltage ~ Heating LHC cycle with 2 injections in the SPS Thermiomic Em.Current

10. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 9/16 Ferrite Effects

11. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 10/16 Hot wire radiation profile Digitized video recording of an 8 mm carbon wire scanning a 0.8 mA electron beam (LEP). The wire is parallel to the horizontal axis, and the light intensity is plotted along the vertical axis (arbitrary units). Successive profiles are separated by 20 ms. The central spot corresponds to the passage of the wire through the beam.

12. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 11/16 Ferrites in SPS

13. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 12/16 LHC WS tank

14. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 13/16 Requirements 1/2 Wire speed (actual range from 0.1 to 20 m/s): –High: Wire damage. Magnet quench. –Low: PMT signal statistics. Position measurement statistics. Wire diameter (actual range 8-30 µm): –Large: Scintillator signal statistics. Ease of handling. –Small: Magnet quench. Wire material (tried C, SiO 2, SiC, Be, W): –Conducting: Continuity monitoring. Temperature monitoring. –Resisting to high beam intensities and RF power coupling.

15. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 14/16 Requirements 2/2 Mechanics: –Rigid: Vibrations, deformations. Position measurement. –Linear: Straight forward position measurement w/o conversion factor errors. Fork: –Opening ranging from 28 (LEP) to 200 mm (SPS). –No Al for LHC. Scan timing inaccuracy < 1ms. Position measurement inaccuracy ~ 1µm.

16. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 15/16 Suggestions for a new design 1/2 A wire of 100mm long and 30um of diameter only weights ~160 µg! –Design a light weight wire transport system for high speed (=acceleration). –Need lower force to move this at high speed. –Lower force induces less vibrations. Try to avoid bellows. –Fragile. –Need high forces. Position measurement as close as possible to wire fixation. Design small (RF friendly) wire cavity. Use position instead of speed feedback.

17. AB/BI J. Koopman New WS design - Brain storm session 18/06/2007 16/16 Suggestions for a new design 2/2