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Radiator study status

Radiator study status. B2GM, 6 th July. Y. Horii, Y. Koga, N. Kiribe , … (Nagoya University, Japan). Introduction. Performance of TOP shown in TDR Problem arising from the beam test in 2010:. Simulation.

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Radiator study status

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  1. Radiator study status B2GM, 6th July Y. Horii, Y. Koga, N. Kiribe, … (Nagoya University, Japan)

  2. Introduction • Performance of TOP shown in TDR • Problem arising from the beam test in 2010: Simulation Very effective for many modes including K±/p±while it is challenging to achieve this performance. Time difference of the time distributions from TDC between simulation and data. Data Radiator study is important for investigating the reason. Time (M. Thesis by Y. Arita)

  3. Radiators mirror • Radiator for beam test in 2010 • Two “Suprasil-P20” bars and mirror,surface polished by Okamoto. • Radiator for beam test in 2011 (backup for Belle II TOP?) • One “Suprasil-P710” bar polished by Okamotoand one “Corning-7980” bar polished by Zygo. • Mirror and wedge will also be glued. glue Suprasil-P20 glue Suprasil-P20 Already glued and there are restrictions for the checks… Suprasil-P710 Corning-7980 Will receive the Suprasil-P710 in the middle of July. mirror Today we will show the status of the quality check for the Corning-7980. wedge

  4. Photon paths and their effects Striae and surface non-flatness of quartz and mirrorcould change the paths of the photons. If this change is large compared to the PMT SPEC,effect on the K/p separation could be significant. PMT resolution: ~40 psec channel size: ~5 x 5 mm2 1 mradchange at ~1m before arriving at PMT produces Time difference~ 1 mm / c ~ 3 psec Position difference~ 1mm Finally we need to estimate the effect by the simulationbut at least the variance of O(0.1) mrad will be safe.

  5. Check of the photon paths Data taken by CCD. Example of the images at the CCD: Striae and surface non-flatness effecton position and size of the spot. Laser (405 nm) Data Fitted PDF Bit map file is transferred toa histogram and fitted with2-D Gaussian (signal)+ 2-D linear function (BG). Only Blue is used from RGB.

  6. Check of the photon paths CCD my [mm] sy [mm] 1.2 m y [mm] y [mm] Laser y mx [mm] sx [mm] x Scanned incident points atx=2.5 cm. y [mm] y [mm] y >15 mm: through air. y <15 mm: through bar. Variance is obtained for y = 14 mm. (Variance due to non-zero incident angle.) (Could be the lens effect from the bar.) (Thickness of the bar in y axis is 2 cm,and length of the bar in x axis is 45 cm.)

  7. Scan for x axis • As a further check, we take dataalso for x = 12.5, 22.5, 32.5, and 42.5. y x We show the position (mean of Gaussian) in y axis for each x value. x = 12.5 cm x = 22.5 cm x = 32.5 cm x = 42.5 cm my [mm] my [mm] my [mm] my [mm] y [mm] y [mm] y [mm] y [mm] Quite similar results are obtained for all y points. Obtained variances correspond to 1 mrad shift of the photon direction.

  8. Surface flatness of the bar • Surface flatness of the bar is measured by Zygo. y x Flatness for vertical (y) axis. Flatness for horizontal (x) axis. 1 mrad shift of the photon direction can be made by the non-flatness of the surface. Then we conclude that the effect of striae on the measurements in page 6 and 7arelower than (or in a similar level to) the effect of the non-flatness.

  9. Another check: bulk transmission I1 y Scanned incident position for x and y. I3 x I0 and I1 measured by PD. I2 and I3 calculated by Fresnel equation. I0 I2 Laser (405 nm) Systematic error is not estimated yetbut it will be around 0.01 (PD efficiency). Bulk transmission (per meter) ismeasured to be around 0.98-0.99. Photon retainment after 10 m is 80%-90% (safe).

  10. Similar measurements for Suprasil-P20 • While the bars are already glued for Suprasil-P20,we measure the change of photon direction and bulk transmissionsimilarly by using the laser from the side. mirror glue glue mx [mm] sx [mm] Laser CCD, PD y [mm] y [mm] 40 cm my [mm] sy [mm] Change of photon direction is O(0.1) mrad.(Effect of striae is smaller than the one of non-flatness.) Bulk transmission is 1.00±0.01 (safely large). y [mm] y [mm]

  11. Summary and plan • Effects of the striae and the non-flatness of the surfaceareestimated by measuring laser light by CCD. • No significant effect of striae is obtained for the Corning-7980 and Suprasil-P20 bars for now. • We will receive the Suprasil-P710 bar in the middle of July.Need to check the quality soon after that. • We need to make a decision on the bar in this summerfor ordering the mass production for Belle II.

  12. Backup slides

  13. Plan July Week 1 Busy with BGM/B2GM Week 2 Joint the mock-up (glass) bars. Week 3 Quartz quality check. Week 4 Joint the quartz bars.

  14. Issues • Bulk • Bulk transmission (photon retainment) • Mean and width of the laser spot (mean and width at PMT) • Surface • Surface reflectivity (photon retainment) • Mean and width of the reflected spot (mean and width at PMT) • Mirror • Reflectivity (photon retainment) • Mean and width of the reflected spot (mean and width at PMT) • Glue • Refraction index (reflections at glue joints provide backgrounds) • Position dependence for all measurements. • Numerical estimation of the effect of each source to PID power.

  15. Light path in the bar Striae and surface irregularities of quartz and mirror could change the paths of the photons. Light path Want to know the effects on position and timing at PMT. mirror images of the bar

  16. Naïve estimation 1 m 1 mrad PMT resolution: ~40 psec channel size: ~5 x 5 mm2 1 m Time difference~ 1 mm / c ~ 3 psec Position difference~ 1mm

  17. Bitmap  Text Reported on 23rd May (Mon). Order is “BGR.” 

  18. Text file  Root file • The text file is converted to a root file which includesthree TH2I objects (histograms for blue, green, and red). blue green red Since the wavelength of the laser is 405 nm,we obtain the highest peak for blue.

  19. 2-D fit for the blue histogram Hist. for blue Fitted PDF PDF Signal: Gauss(x) xGauss(y) BG: Linear(x) xLinear(y) Proj. for x Proj. for y c2/ndf = 0.19 c2/ndf = 0.63 Small values of c2/ndfindicate good quality of the fit.

  20. More projections Slightly enhanced for lower x.Effect of the light from outside of the clean room?(Anyway, is it not significant for now.)

  21. Bulk Transmission DIRC(Babar) results 99.9±0.1%/m (442nm) 98.9±0.1%/m (325nm) ・Using the photo diode, measure the intensity for I1and I2. ・ We can calculate I3and I4 from Fresnel theory. n1=1.47 (405nm) n0=1.00 405nm ・Then obtain the ratio = I2 / (I1 – 2 I3) 40cm PID Upgrade Meeting, 27th May

  22. Setup Laser PD PID Upgrade Meeting, 27th May

  23. Results x(mm) QuartzBar mirror DIRC(Babar) results 99.9±0.1%/m (442nm) 98.9±0.1%/m (325nm) I1 = 57.28±0.133 μA I2(Average)=53.13μA Theoretical value of surface reflection ratio R=3.62％(α=0) Bulk Transmission 100.0±0.3％（40cm） 100.0±0.8(%/m) PID Upgrade Meeting, 27th May

  24. Suprasil-P20 Local roughness is O(1) Å. Global flatness is O(1) mm.

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