LIU-PSB Review on H-/H0 dumps – 18 th April 2013 H-/H0 current monitor F. Zocca, F. Roncarolo, B. Cheymol, A. Ravni, S. Burger, G.J. Focker, J. Tan BE/BI

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Concept H 0 / H - current monitor needed in front of the dump - to allow efficient setting up of the injection - to monitor the efficiency of the stripping foil (detect degradation and failure) DUMP H 0 monitorH- monitor POLARIZATION FRAMES for secondary emission suppression Titanium, negative High-Voltage (-1kV), 1 mm thick Titanium plates, grounded (0V), 1 mm thick The H 0 /H - current monitors are supposed to be plates intercepting the H 0 and H - ions and acting as a Faraday cup for the stripped electrons (stripping & collection) Design principle

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 General specifications  Robust and simple (lifetime ≈ 20 years, no maintenance)  Radiation dose of MGy per year  Vacuum level mbar with beam  Withstand the BSW4 pulsed magnetic field of 0.4T and at the same time do not perturb the field by more than ≈ 0.1 %  Transverse dimensions (including support structure) not exceeding dump dimensions  Sensitive areas maximized to cover as much as beam halo as possible  Withstand the heat load in normal operation condition and a full Linac4 pulse load (2.5×10 13 H- ions), in case of failure of the stripping foil, on a one-off basis, several times per year  Dynamic range: 5×10 7 – 5×10 12 ions (for H- and H0 alike)  Absolute accuracy ± 20 %, relative accuracy ± 10 %  Time resolution: integral over the full injection time (few  s – 100  s) – however higher resolution is welcome

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Plates material: titanium Material Conductivity (1/  m) (for signal read-out) Thermal load (  T) for a full Linac4 pulse Melting point Neutron yield (w.r.t. n° of protons) Signal Q (e/H - ) with NO external fields* Signal Q (e/H 0 ) with NO external fields* Compatibility with BS4 field Graphite 6.1 × K3773 K0.41 % YES Aluminum 3.77 × K933 K0.57 % NO Titanium 2.34 × K1933 K0.99 % YES Copper 5.96 × K1356 K1.0 % NO Tungsten 1.89 × K3683 K6.4 % NO Fully acceptable Acceptable (not ideal) Not acceptable Among low-Z conductive materials, titanium is the only one with acceptable impact on the BS4 field quality thanks to the relatively “low” conductivity Requirements: good enough conductivity (for signal read-out) but compatible with BSW4 field quality, low thermal load, low neutron yield (low activation), high signal level * taking into account losses due to electron backscattering and secondary emission

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Charge signal estimate Q (e/H - ) = -2*(1-  ) + 2*SEY P + 2*SEY BS + Y D Q (e/H 0 ) = - (1-  ) + SEY P + SEY BS + Y D  fraction of backscattered electrons (e - energy range ≈ 1-87 keV) SEY P = Secondary Emission Yield of the Proton (e - energy range ≈ 1-20eV) (SEY of H- entering the plate = SEY of proton exiting) SEY BS = Secondary Emission Yield of one BackScattered electron Y D = fraction of “delta-rays” electrons emitted by the plate owing to collisions with the proton beam (e - energy range ≈ keV) Proton energy = 160 MeV  electron energy = 87 keV Material  SEY P SEY BS YDYD Q (e/H - )Q (e/H 0 ) Titanium

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Backscattering coefficients for different materials MaterialBS coeff Carbon (graphite) 5.2 % Aluminum14 % Titanium23 % Copper29 % Tungsten48 % Al Oxide11 % Ti Oxide17 % FLUKA simulation : 87 keV electron beam on a 1mm thick plate Simulations in agreement with literature data: E.H. Darlington “Backscattering of keV electrons from thick targets”, J.Phys.D:Appl.Phys., vol 8, Energy distribution of the backscattered electrons normalized to the number of primaries

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Effect of plate oxidation on the BS coeff Ti oxide layerBS coeff 0 nm (Ti plate) % 10 nm23.20 % 50 nm23.01 % 100 nm22.78 % 500 nm22.66 % 1 um22.31 % 5 um19.75 % 10 um17.44 % 50 um17.10 % 100 um17.09 % 1 mm (Ti oxide plate) % FLUKA simulation (87 keV electron beam): 1 mm Titanium plate + surface layer of Ti oxide of different thickness 87 keV electron range in Ti = 25 um  backscattering is a “bulk” effect rather then a “surface” effect (mainly takes place within a distance of 1 to 10 um from the surface)  a typical oxidation layer of several nanometers does not affect significantly the BS coefficient for 87 keV electrons

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Y D : “delta-rays” electrons Yield FLUKA simulation (B. Cheymol): 160 MeV proton beam  electron yield of 2-3% (w.r.t. the proton-primaries) not much depending on the plate material Energy distribution of the delta-rays electrons exiting a titanium plate Electrons created by elastic collisions Electrons created by pair production T max = 378keV : maximum energy transfer to a free electron by a 160 MeV proton NB: for the calculation of the charge collected on the plate, the SEY due to these high-energy electrons can be considered negligible zoom

Linac 4 current (average during pulse) = 40 mA Number of particles per pulse = 1×10 14 Max number of particles per pulse per PSB ring = 2.5 × Stripping foil of ≈ 200  g/cm 2 :  H- stripped to H0 ≈ 1 %,  H- stripped to H+ ≈ level BUT assume that 1% of H- from the LINAC4 beam will miss the foil and impact the dump  nominal number of particles hitting the monitor per injection = 2.5 × for H0 and H- alike F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Expected signals (1) Minimum sensitivity = 5 × 10 7 particles per injection (to resolve a change in the unstripped H0 beam flux of about of the full injected beam, and about 1% of the lowest intensity beam) Maximum intensity = 5 × particles per injection(20 % of the full injected beam, in case of dropping stripping efficiency) Desired dynamic range = 5 × × particles (for H- and H0 alike)

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Expected signals (2) Q (e/H - )Q (Coul) MINQ (Coul) NOMQ (Coul) MAX H- SEY + BS + Y D  * * *10 -6 BS + Y D  * * *10 -6 Full deposition  * * *10 -6 H0 SEY + BS + YD  * * *10 -6 BS + Y D  * * *10 -6 Full deposition  * * *10 -6 Q (e/H - ) Average Pulse Current MIN Average Pulse Current NOM Average Pulse Current MAX H- SEY + BS + Y D  nA0.56 mA11 mA BS + Y D  nA0.6 mA12 mA Full deposition  nA0.8 mA16 mA H0 SEY + BS + YD  nA0.28 mA5.6 mA BS + Y D  nA0.3 mA6 mA Full deposition  -180 nA0.4 mA8 mA

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Monitor geometry preliminary proposal Top view Signal plates Polarization frames Missing on the front frame only

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Polarization rings: E-field effect frame ( V) View from the top monitor plates Simulations including surrounding beam pipe E-field map on the monitor plates Effect due to the missing lateral frame CST Particle Studio tracking simulation Electron energy range = eV Isotropic angular distribution Stationary condition No space charge

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 E-field + B-field effect (BSW4 magnet 0.4T) Uniform vertical B-field of 0.4 T Stationary condition, no space charge Secondary emission electrons (10 eV - 30eV) Curvature radius for 30eV electrons ≈ 30  m Backscattered electrons (60 keV – 90 keV) Curvature radius for 90keV electrons ≈ 2.6 mm “Delta-rays” electrons (125 keV – 375 keV) Curvature radius for 375 keV electrons ≈ 6 mm 10 mm

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Beam vertical envelope Vertical Circulating Betam4.1 Beta-beat%25 Max betam5.125 Mismatch1.4 Betatron env. 4sigmamm9.65 Dispersionm0 Dp/p Max. momentum displacementmm0 Mech. Tol.mm1 orbitmm2.20 Max. offset for paintingmm8.00 Max. Beam env.±mm20.9 Tot. envelope mm 42 Vertical Injected Betam8 Betatron env. 98%6.35 Dispersionm0 Dp/pmm0.00 Max. momentum displacementm0 Mech. Tol.mm1 Delivery precisionmm1 Max. offset for paintingmm10 Max. Beam env.±mm18.3 Tot. envelope mm 37 Emittance = 0.35 mm mrad (instead of previous 0.5 mm mrad) Courtesy of C.Bracco - TE/ABT 2.5  (98 %) 4 

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Beam horizontal envelope Emittance = 0.35 mm mrad (instead of previous 0.5 mm mrad) Courtesy of C.Bracco - TE/ABT Horizontal circulating Betam5.6 Beta-beat%25 Max betam7 Mismatch1.34* Betatron env. 4sigmamm10.80 Dispersionm1.4 Dp/p Max. momentum displacementmm6.16 Mech. Tol.mm1 orbitmm4.00 Max. offset for paintingmm2.00 Max. Beam env.±mm24.0 Tot. envelope mm 48 Horizontal injected Betam10 Betatron env. 98%mm5.92 Dispersionm1.4 Dp/p Max. momentum displacementmm6.16 Mech. Tol.mm1 Delivery precisionmm1.00 Max. offset for paintingmm2.00 Max. Beam env.±mm16.1 Tot. envelope mm 32 Before 56 mm Before 34.8 mm * Old data  (98 %) 4 

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Courtesy of C.Bracco Beam horizontal envelopes SiC Dump 110 mm + 30 mm Pol. Frames

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Courtesy of C.Bracco Beam horizontal envelopes SiC Dump 110 mm + 30 mm Pol. Frames Separation H0/H+ = 2.8 mm Distance dump edge/ H0 beam = 0.5 mm Separation H0/H- = 10.8 mm

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Courtesy of C.Bracco Beam horizontal envelopes C Dump 160 mm + 30 mm Pol. Frames Separation H0/H+ ~ 1.1 mm (!) Distance dump edge/ H0 beam = 0.5 mm Separation H0/H- = 9.2 mm

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 How to fix the monitor to the dump Molybdenum (?) inserts, with holes, brazed on SiC dump Macor (or Chromox = chromium-doped alumina) arms screwed on the inserts and holding the monitor screw detailFinal view inside the pipe Preliminary proposal (by A.Ravni) in case of SiC dump

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Electronics read-out & cabling  Charge integration or current read-out: choice may depend on the amplitude of the signals induced on the plates by the circulating proton beam (to be checked)  Control signal needed for start-stop integration/current read-out, according to the injection time window  Cables: mechanical stability and long-term reliability (20 years life time…) - rigid/semi-rigid ceramic-insulated rods/cables - option: ceramic powder around the conductor (LHC schottky monitors) - 3mm diameter to be allocated for each cable - possibility of embedding cables in the dump (grooves) to be investigated  2 cables for signal read-out (H- and H0)… + 2  redundancy needed ?  2 cables for high voltage (-1kV) to polarize the frames  2 cables for test signals? (to inject a test current on the plates by means of a small resistance connected to the internal side of the feed-through)  2 (+4?) BNC + 2 SHV feed-through on the flange (all not ground-insulated) Minimum: 4 cables --- Maximum: 8 cables

F.Zocca - LIU-PSB Review on H-/H0 dumps – 18 th April 2013 Conclusions & outlook  Material choice  Design principle  Range of expected signal intensities  Final precise dimensions (w.r.t. dump size & beam dynamics simulations)  How to fix the structure to the dump  Final simulation of the impact on the BSW4 field (by magnet group)  Cables type and quantity  Final integration in the system (design office)  Read-out electronics We have finalized: On-going developments: