Report from Fermilab: Beam Tests and QUARTZTOFs Mike Albrow (Fermilab) (if you heard this in September, not much new!) Beam tests with 2 Burle 25 um-pore with in-line quartz radiator with Photek 4 um MCP-PMT Design and construction of two QUARTZTOF detectors. What we learned from beam tests. Plans … next steps

Argonne – Chicago – Fermilab Picosecond Timing Collaboration Tests at Fermilab Test beam August 2008 Who: Mike Albrow, Ed May, Tyler Natoli, Erik Ramberg, Anatoly Ronzhin, Jerry Va’vra, + Camden Eartly, Henry Frisch, Scott Wilbur, .. (1) Burle, head-on (2) QUARTZTOFs MCP-PMT Off-axis parabolic mirror Half-cone radiator Works, but cannot be close to beam (unless edgeless MCP-PMT developed) … even then. Can be very close to beam (edgeless) Several times more light, prompt. PMT far from beam. Still to be demonstrated.

Fermilab test beam is nicer than CERN’s ! 120 GeV protons. Camden Eartly (Chicago) Jerry Va’vra (SLAC) Anatoly Ronzhin (Fermilab)

I am not going into the electronics … .high end commercial Commercial electronics (ORTEC) Calibrated TDC : 3.1 ps / channel We (both Chicago and Fermilab) are developing chips that could be actually used in FP420 (25 ns/crossing) with some waveform digitization.

Test electronics resolution by splitting a signal (high bandwidth splitter circuit). = 6.4 ps ADC1 should = ADC2 Not quite: ADC imperfections. Probably not important. per channel = 4.6 ps

= 14 ps 2x2 pads =12mm x 12mm = 21 ps = 13 ps (per detector) Initial dt, 2 25 um Burle tubes + 6 mm Quartz plate + 2mm window Cut out tails of ADCs (some multihits) = 14 ps 2x2 pads =12mm x 12mm Apply small PH slewing correction = 21 ps = 13 ps (per detector)

Need optical contact or light is TIR for TIR at back Note: 6mm with n = 1.415 dt(F-B) = 20 ps Need optical contact or light is TIR 6mm PMT p

~ 15K – 20K each! Thanks to Photek (UK) for loan of two PMT210’s 2-stages:10mm diam Photek Microchannel Plate PMT TTS (single p.e.) ~ 20 ps 100 prompt p.e. ~ 2 ps ~ 15K – 20K each! Thanks to Photek (UK) for loan of two PMT210’s

Photek (UK) single channel MCP-PMTs 210 (2 plates, 10 mm diameter, ~4 um pores) Loaned 2, 1 would not take HV. Put other with Burle tube already tested. No extra radiator, just 5.6 mm quartz window. Burle Photek ADC cut (Photek cleaner) dt after ADC cuts. (Photek + electronics) = 11 ps (Photek alone) ~ 8.8 ps

We are there! & need to get PMT away from beam! Could simply feed signal to ~ 4 channels, Reduce electronic contribution (Could be 7.4 ps w/ tighter PH cuts) Jerry Va’vra & need to get PMT away from beam! We are there! BUT … This geometry is not edgeless … we must have <~1mm edge

We had also Photonis ( “Burle”) 10 um tubes, but these had poorer PH spectra and actually worse probably less prompt light.  GET LIGHT! Also we (Anatoly Ronzhin) tested some 3mm x 3mm SiPMs with 16 mm (too much) Plexiglas radiator in front. ~ 47 ps, per device. Far to go, but interesting. Thin and fairly edgeless, also “cheap” (cf. MCP-PMT) Can have many (e.g. 16) in series. But probably rate problems for FP420.

An isochronous & achromatic Cerenkov Counter A possible solution to the edgelessness requirement (more light too!): QUARTZTOF (M.G.A.) An isochronous & achromatic Cerenkov Counter Making Cerenkov light parallel  point focusing New design/concept for fast timing Cerenkov counter Much more light. Edgeless. PMTs far from LHC beam Ray-tracing calculations done: Expect > factor 10 more photoelectrons than either GASTOF or QUARTIC Photons arrive promptly (< few ps) at MCP-PMT Full (wavelength-dependent) simulations largely done. Needed for [x,y] position dependence over [2mm x 20mm] area. Two made for beam tests (in August at Fermilab).

Fast timing detectors tested in beams, in FP420 R&D report: 1) GASTOF (KP, Louvain) 2) QUARTIC ( MGA Fermilab, AB UTA, JP Alberta) ++ 20 cm GASTOF with Atmospheric C4F8O  ~ 10 p.e. nearly all collected, within few ps QUARTIC bars ~ (inclined) 9 mm  ~ 120 pe, but solid angle for direct light small,  ~ 3-4 pe/bar (in tests) QUARTZTOF: Radiator 20-30 mm quartz, nearly all light collected within a few ps. > 200 p.e. (At least for 2 mm x 2mm “sweet spot”)

QUARTZTOF (QT) Principle Apex – base distance is L is “isosceles point” p (“needle” beam ~ 2mm x 2mm) FP420: 2mm x 20mm L and all emission points in between Proton along axis of cone, with half angle = half Cerenkov angle. All Cerenkov light emitted (all ) up to isosceles point L is totally internally reflected out through the base and arrives simultaneously, in a parallel beam. It can thus be focused to a point by a 90deg off-axis parabolic mirror. Cannot use full cone in FP420, but cut in half.  True for “lucky wavelength” … but can compensate for others.

GEANT Simulation – Kristina Yancey (summer student, +Hans Wenzel) Enables studies of x,y dependence Wavelength dependence of emission, absorption, reflection, QE Arrival time distribution vs radius at photocathode  Compensating “wedge” at MCP front face. MCP-PMT Photocathode Cone optimized for 689 nm (1.8 eV) Cone angle 23.3° Off-axis Parabolic mirror Focal Length = 76.2 mm Off-axis Parabolic Mirror Absorbing Cylinder Quartz Cone

Transmission of UVT Plexi sample We used a spectrophotometer to measure the transmittance of 200 nm – 800 nm light through 2 x 10 mm blocks, and the two together. Irina Kubantseva Data sheet: … goes into simulation.

Fantastic for perfectly on-axis Very position-sensitive X = +1 mm On axis Here’s the issue: Fantastic for perfectly on-axis Very position-sensitive X = +2 mm

Need larger MCP for coverage (1,0) (0,0) (2,0) Aperture of Photek 10mm Aperture of Burle- Photonis 48x48 Need larger MCP for coverage

GEANT: Arrival time, optimal wavelength with 0,1,2 mm shifts off axis +1 mm (in x) On axis σ =0.3 ps +2 mm in x 14 ps

Time as a function of radius Wiggles not real 10 ps

Arrival Time after correction by t(r), within r=4 mm

GEANT: Arrival time vs wavelength; focusing red light ~ MCP cut-off Light at larger radii Light at center spot 10 ps 2.5 ps This can be compensated for with a wedge It’s the jitter in the rise time that counts, and we know the position of the p.

Select light with λ > 450 nm: GEANT Select light with λ > 450 nm: 1 ps σ(t) = 1.1 ps, 457 photons (1 proton)  ~ 75 p.e. But we can use also the light with λ < 450 nm !

GEANT: Time front light vs x,y position wrt cone axis 10 ps At least 4 mm x 4 mm is OK

CAD of Test Beam setup (John Rauch, FNAL) Can mount Cylindrical Photek, Square Photonis, SiPMs Installed in black copper-lined box with feed-throughs. Precision alignment, & dz shifts Design & Construction (Carl Lindenmeyer, John Korienek, FNAL) Conical radiator Precision mechanics Off-axis parabolic mirror

Test beam modules with Burle tubes. 2x2 pads = 12mm x 12 mm together Provision to adjust focus, and separation between QUARTZTOFs (10mm = 33.3ps) All placed in Cu-shielded dark box, lined with special light absorbing paper.

Optical checks post-TestBeam Observe waves on milled conical surface: May need “optical” flatness, polishing

Striations from ripples (not clear in photo) LASER BEAM 38° 2°

Multiple QTs Depending on performance over full x-range (~ 20 mm) We may want a few (~ 4?) in series. Full depth/30 mm radiator ~ 10 cm Optimum may be 15-20 mm radiator, it scales. Schematically: Multiple measurements good, at least one is optimum. Also note: The ~ parallel beam from the parabolic mirror could (?) be 10’s of cm long, so MCP’s and electronics far from beam.

Remarks Fast timing is crucial for FP420 to work. 15-20 ps may be OK for L = few x 10^33 but <~ 10 ps needed for 10^34 We have not demonstrated that yet, but we can see a way and we progress. I am optimistic about conical QUARTZTOF, even if “sweet spot” is only a few mm^2 it should be much better than GASTOF and QUARTIC. But we have to demonstrate it. May need optical quality cone surface, and large area (~ 50 x 50 mm) MCP-PMTs. Longer term there could be solutions for multiple p-measurements within a bunch crossing … Streak Camera with pixel detectors. (KP idea). Concept is there … should work in principle … some years to develop? Perhaps < 5 ps timing is possible if electronics up to it (25 ns) Perhaps multiple protons can be measured eventually.

FSC = Forward Shower Counters Mike Albrow, Fermilab What: We propose to install a set of scintillation counters around both outgoing beam pipes, ~ 60m – 85m Why: (a) As veto in Level 1 trigger to reduce useless pile-up events. (b) To detect rapidity gaps in diffractive events (p or no-p). (c) Help establish exclusivity in central exclusive channels (d) To monitor beam conditions on incoming and outgoing beams. (e) To test forward flux simulations (MARS etc.) (Can also be used as supplementary luminosity monitors: E&W) N.B. : This will provide valuable tests of radiation environment to be expected for FP420. Terra incognita

Location of FSC counters (before connecting vacuum pipe installed) Warm accessible vacuum pipe (circular – elliptical) Do not see primary particles, but showers in pipe ++

Bunches spaced by 25ns = 7.5 m dt = 3.333ns x z(mod7.5m) e.g. z = 59.426m dt=1.9ns z = 85.126m dt=8.8ns Z1, bunches Simultaneous As at z = 0 time Z2, bunches separated in t z 4 shown, could be 5 or 6

Efficiency for detecting forward particles (Orava): Low- : > 20% for > 9.0, > 60% for 9.5 < < 11.5 (integrated over pT)

Summary on FSC: We want to add FSC to both sides of CMS, before first collisions. Either or both of Scintillators and GEMs. Greatly improving Diff triggers, and especially central exclusive studies Early presentation to CMS, but not yet formally proposed. Meeting this week in CMS week.