J.J. García-Garrigós Septiembre 2008

1. Design and Construction of a Beam Position Monitor Prototype for the Test Beam Line of the CTF3 J.J. García-Garrigós Septiembre 2008

2. Contents Introduction: Linear Collliders The CLIC and CTF3 The BPS monitor prototype in theTest Beam Line BPS mechanical design BPS sensing mechanism and general description BPS electronic design BPS wire test results and analysis Conclusions and Future work BPS-TBL-CTF3 J.J. García-Garrigós

3. Present and Future Colliders • The LHC will probe the new “terascale” energy region : • Confirm or refute the existence of the Higgs boson to complete the Standard Model • Explore the possibilities for physics beyond the Standard Model, such as supersymmetry, extra dimensions and new gauge bosons Particle physics community worldwide have reached a consensus that the results from the LHC will need to be complemented by experiments at an electron-positron collider operating in the tera-electron-volt energy range BPS-TBL-CTF3 J.J. García-Garrigós

4. Why e+ e- Linear Colliders Some physics reasons • p-p colliders can reach higher energy than e+e-, but • the energy of the constituents (quarks and gluons) are lower • p-p interaction is too complicated (not easy to analyze collision data) • e+e- colliders: • cleaner experimental enviroments • available eγ, γγ and e-e- interactions • available polarized beams • p-p and e+e- complementary • particle discovery by p-p colliders • finer study by e+e- colliders  Naturally arise as LHC successors BPS-TBL-CTF3 J.J. García-Garrigós

5. Why a Linear Collider, and not just build a bigger Storage Ring 500 GeV LC LEP at CERN, CHEcm = 180 GeVPRF = 30 MW Livingston Chart BPS-TBL-CTF3 J.J. García-Garrigós

6. Why a Linear Collider, and not just build a bigger Storage Ring Synchrotron radiation from an e- in a magnetic field: average power Energy loss per turn of a machine with an average radius r : • LEPe+e- storage ring: • The biggest superconducting RF system with3640 MV per revolutionjust enough to keep the beam in LEP at its nominal energy Energy loss per turn has to be be replaced by the RF system, which is the major cost factor for a collider. BPS-TBL-CTF3 J.J. García-Garrigós

7. bang! Why a Linear Collider, cause no bends, but also needs lots of RF! e+ e- 5-10 km • No Synchrotron Radiation, but new problems arise: • we cannot store the beams, LC is one-pass device where the beams must be accelerated to the required energy on each pulse of the machine • we cannot take advantage of the stored beam to slowly ramp the energy up, we have to provide several Km of RF Power (25-100 MV/m) to achieve the energy in a single-pass BPS-TBL-CTF3 J.J. García-Garrigós

8. Now, no losses And we can get the RF Power ¿ ? Future Linear Colliders The CLIC scheme is based on normal conducting travelling-wave accelerating structures, operating at a frequency of 12 GHz and with very high electric fields of 100 MV/m to keep the total length to about 48 km for a colliding-beam energy of 3 TeV. This study is based on an RF system using superconducting cavities for acceleration, with a nominal accelerating field of 31.5 MV/m and a total length of 31 km for a colliding-beam energy of 500 GeV. Feasible Proof of Principle BPS-TBL-CTF3 J.J. García-Garrigós

9. CLIC: The Compact LInear Collider Each sub-system pushes the state-of-the art in accelerator design The peak RF power required to reach the electric fields of 100 MV/m amounts to about 275 MW per active meter of accelerating structure. Not possible with klystrons. Hence a novel power source, an innovative two-beam acceleration system, in which another beam, the drive beam, supplies energy to the main accelerating beam. BPS-TBL-CTF3 J.J. García-Garrigós

10. CTF3: The CLIC Test Facility 3 • To demonstrate the Two-beam acceleration scheme. • A scaled facility for one branch of the Drive Beam Generation System Layout of the CLIC EXperimental area (CLEX) building with TBL BPS-TBL-CTF3 J.J. García-Garrigós

11. TBL: The Test Beam Line 16 TBL Cells • The main aims of the TBL: • Study and demonstrate the technical feasibility and the operability a drive beam decelerator (including beam losses), with the extraction of as much beam energy as possible. Producing the technology of power generation needed • for the two-beam acceleration scheme. • Demonstrate the stability of the decelerated beam and the produced RF power by the PETS. • Benchmark the simulation tools in order to validate the corresponding systems in the CLIC nominal scheme. BPS-TBL-CTF3 J.J. García-Garrigós

12. TBL + BPM specifications • Main features of the Inductive Pick-Up (IPU) type of BPM: • less perturbed by the high losses experienced in linacs; • the total length can be short; • it generates high output voltages for typical beam currents in the range of amperes; • calibration wire inputs allow testing with current once installed • Broadband, but better for bunched beams with short bunch duration or pulse IPU type of BPM suitable for TBL 2 BPS Prototypes developed at IFIC, scaled and redesigned version of IPU used in DBL of CTF3 TBL beam time structure BPS-TBL-CTF3 J.J. García-Garrigós

13. BPS Mechanical Assembly PCB plates Ferrite cylinder Vacuum assembly: ceramic tube with Kovar collars at both ends, one collar TIG welded to the downstream flange, and the other one electron welded to a bellow and a rotatable flange. ~10-10 mbarl/s [High Vacuum] Cooper body BPS-TBL-CTF3 J.J. García-Garrigós

14. BPS Basic Sensing Mechanism Primary transformer electrode Longitudinal cross-section view • Four Outputs with two Calibration inputs: • [V+,V-, H+,H-] and [Cal+, Cal-], respectively • Difference signals (Δ) normalized to sum signal (Σ) proportional to beam position coordinate, • xVα ΔV /Σ [Vertical plane] • xHα ΔH /Σ[Horizontal plane] • where: ΔV ≡(V+ − V-);ΔH ≡(H+ − H−); • and,Σ≡(V+ + H+ + V− + H- ) BPS-TBL-CTF3 J.J. García-Garrigós

15. BPS Readout chain Amplifier developed at UPC by G. Montoro Digitizer/ADC developed at LAPP(Annecy) Both Designs must be Rad-Hard BPS-TBL-CTF3 J.J. García-Garrigós

16. Typical IPU Frequency Response Induced current/signal Pulse deformation τdroop =1/ ωlow, and τrise =1/ωhigh To let pass the pulse without deformation Droop time very important for ADC sampling. τdroop ~ 102 tpulse τrise ~ 10-2 tpulse ωlow = R/L, and ωhigh = 1/RCS BPS-TBL-CTF3 J.J. García-Garrigós

17. BPS Electronic design PCBs Schematics and Output relation Vsec = (RLoadRS1/(RS1+RS2+RS1)N) Ielec ≡ (Σ/IB) Ielec with: (Σ /IB)= 0.55Ω for the design values: RLoad = 50 Ω, RS1 = 33 Ω, RS2 = 18 Ω and N = 30 turns Characteristic Output Signal Levels: For a beam current of: IB = 30A Σ = 16.5 V [outputs sum] Vsec = Σ /4 = 4.125V [centered beam] ||ΔV||max = ||ΔH||max = Σ /2 = 8.25V [beam at elec] BPS-TBL-CTF3 J.J. García-Garrigós

18. carried out during several short stays at CERN, in the AB/BI-PI[1], where the wire testbench is placed, and it has been previously used for testing and calibrating BPMs for the Drive Beam Linac (DBL) of the CTF3. BPS1 Characterization Tests [The Wire-Test]* Sensitivity and Linearity + Frequency Response Tests carried out during several short stays at CERN, in the AB/BI-PI* Labs (Bldg.37) Testbench used to characterize the BPMs for the Drive Beam Linac (DBL) of the CTF3 *With the help of: CTF3 Collaboration * Accelerator an Beams Department/ Beam Instrumentation Group – Position and Intensity Section BPS-TBL-CTF3 J.J. García-Garrigós

19. Sensitivity and Linearity Test Results Electric Offset Sensitivity Linear fit equations Electric Offset for V,H planes Sensitivity for V,H planes SV = (41.09±0.08)10−3 mm−1 EOSV= (0.03±0.01) mm EOSH = (0.15±0.02) mm SH = (41.53±0.17)10−3 mm−1 BPS-TBL-CTF3 J.J. García-Garrigós

20. Sensitivity and Linearity Test Results Linearity errorOverall Precision/Accuracy Typical S-shape σH = 170 μm σV = 78 μm i) Low current in the wire (13mA) vs beam 32 A σTBL < 50μm BPS above specs ii) Misalignment in the horizontal electrodes BPS-TBL-CTF3 J.J. García-Garrigós

21. Frequency ResponseTest Results Output electrodes ΔV, ΔH and Σ Wire Pos: Center Coupling low freq. components don’t feel the beam variation Wire Pos:+8mm V,H Bandwidth specs: [10KHz-100MHz] tpulse=140ns Cut-off Frequencies: fLΣ = 1.76 KHz fLΔ ≡ fLΔH = fLΔV = 282KHz τdroop Σ = 90usτdroop Δ = 564ns fhigh > 100 MHz, and τrise < 1.6 ns BPS-TBL-CTF3 J.J. García-Garrigós

22. BPS Electric Model Model Cut-off Frequencies: fhigh = 1/2𝜋ReCS • High cut-off frequencyFixed by secondary Cs for all cases • Low cut-off frequenciesTwo different cases: • Centered wire: Balanced wall image curent • Displaced wire: Unbalanced wall image current (low freq. coupling) BPS-TBL-CTF3 J.J. García-Garrigós

23. BPS Electric Model • Centered wire: Balanced wall image curent: • Δ ~0 LΔ= 0 because reflects a coupling in the other case • Low cut-off fixed by LΣ >>LΔ  f Σ << fΔ BPS-TBL-CTF3 J.J. García-Garrigós

24. BPS Electric Model • Displaced wire V,H plane: Unbalanced wall image current (low freq. coupling) • Δ ≠0  LΔ ≠0 appears on the pair of V or H electrodes • Low cut-off fixed by LΔ >> LΣ  fΔ general case and must be compensated by External Amplifier BPS-TBL-CTF3 J.J. García-Garrigós

25. BPS Electric Model • Displaced wire V,H plane: Unbalanced wall image current (low freq. coupling) • Δ ≠0  LΔ ≠0 appears on the pair of V or H electrodes • Low cut-off fixed by LΔ >> LΣ  fΔ general case and must be compensated by External Amplifier BPS-TBL-CTF3 J.J. García-Garrigós

26. Pulse Response and Calibration problem fLΔ[cal] =180 KHz < fLΔ=282 KHz their difference is about 100 KHz. τdroop Δ = 564 ns Represents a problem for the amplifier compensation in the Δ channels, to lower the Δ low cut-off frequency for the wire, fLΔ; because the same compensation designed for the fLΔ will be applied when exciting the calibration inputs to fLΔ[Cal]Bad Pulse for calibration (overcompensation). τdroopΣ= 90 μs τdroopΣ [Cal]= 90 μs • A compromise solution: compensation frequency at the lower one, fLΔ[Cal] Cal. pulse good flatness and wire-beam pulse flat enough for TBL pulse duration(140ns) τdroop Δ [cal] = 884 ns BPS-TBL-CTF3 J.J. García-Garrigós

27. Conclusions and Future Work • A set of two BPS prototypes with the associated electronics were designed and constructed. • The performed tests yield: • Good linearity results and reasonably low electrical offsets from the mechanical center. • Good overall-precision/accuracy in the vertical plane considering the low test current; and, a misalignement in the horizontal plane was detected by accuracy offset and sensitivity shift. • Low frequency cut-off for Σ/electrodes signals, fLΣ, and high cut-off frequency,fhigh, under specifications. • Low frequency cut-off for Δsignals, fLΔ, determined to perform the compensation of droop time constant, τdroopΔ, with the external amplifier. BPS-TBL-CTF3 J.J. García-Garrigós

28. Conclusions and Future Work • Open issues for improvement in the BPS2 monitor prototype: • Correct the possible misalignments of the horizontal plane electrodes suggested in the linearity error analysis. • Check if overall-precisionbelow 50μm (under TBL specs), with enough wire current New wire testbench at IFIC. • Study the different low cut-off frequencies in the calibration, fLΔ[Cal], and wire excitation cases, fLΔ. • Test Beam of the BPS1 in the TBLResolution at maximum current. • BPS’ Series production and characterization (15 more units). The new wire testbench will allow accurate (anti-vibration + micro-movement system) and automatized measurements. BPS-TBL-CTF3 J.J. García-Garrigós

29. Conclusions and Future Work Sketch of New IFIC Wire Testbench. Under development right now. BPS-TBL-CTF3 J.J. García-Garrigós

30. Thanks for your Attention Muchas Gracias BPS-TBL-CTF3 J.J. García-Garrigós

31. BPS1 Characterization Table BPS-TBL-CTF3 J.J. García-Garrigós

32. BPS Monitors Schedule BPS-TBL-CTF3 J.J. García-Garrigós