toru iijima / nagoya top: what has to be done (before decision) bar quality seems to be...

Toru Iijima / Nagoya

TOP: what has to be done (before decision)

Bar quality seems to be satisfactory.

Photodetection is (probably) the most critical issue. TTS Chromatic dispersion optimum QE range Magnetic field immunity Good efficiency ×effective area ratio Position resolution Realistic cost, time for development

High time resolution (pipe-line) read-outBackgroundGeometry

cf.) Npe = 6 with R5900-U-L16 at the beam test

Effective area ~ 40% Collection eff ~ 50%

Toru Iijima / Nagoya (2002.8.31)


Time Resolution w/ PrototypeGreatly improved by better polishing accuracy.t =85ps (L=0.3m), 100ps (L=1m), 150ps (L=2.3m) achieved.

~ Chromatic dispersion limit (almost)

Single pe resolution, bar quality are almost understood.


Bar TOP Beam Test ResultTime resolution t(w/o mirror) = t(w/ mirror)


Application in BelleCorrelation between in and TOP, TOF and Npe.

The most tough part is around in=45°.

35°45° 90° 140°

(T

OP

+T

OF

)/t

Forward photons Backward photons

TOP

TOF

Separation obtained by peN Npe/d~25 (d:bar thickness in cm)


Expected Performance in Belle502K photocathode (green extended bialkari) w/ QEpeak=20%

Bar thickness = 2cm

Bar thickness = 4cm


Photodetector Comparison

1,2,3 have been tested

4: tests are under way

5: B.Dolgoshein (MEPhI, Moscow) et.al., (see SLAC-J-ICFA-23)

Numbers in () are guess, and need be tested or confirmed.

Ceff. x t(TTS) B Gain note

1 R5900-U-L16 50% 1mm 70-80ps × O(106)

2 FM-PMT-L24 85% 1mm 100ps 1.0T O(106)

150ps 1.5T O(106)

3 HAPD (>80%)

OK 100ps OK O(104)

4 MCP-PMT (60%) OK 35ps OK O(106) Life?, Cost?, Size?

5 Si-PM (Geiger mode APD)

30% OK 50ps OK O(106) QE~80% (>500nm), Noise?, size??


MCP-PMTVery good timing performance TTS/photon < 50ps.Tests are underway.

R3809-U50 (Hamamatsu)HV=-3400VMeasured w/ pulse laser (406nm)

ADC

TD

C

ADC TDC

After time walk correction

= 34psSingle pe peakobservable

500ps


Single Photon Time Resolution 3.5GeV/c @ L=0.8m, =45°

Bandwidth (=±100ns, QE=20%

(t)2 = (TTS)2 + ()2Single photon resolution(bandwidth: +-100nm)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

300 350 400 450 500 550 600 650 700 750 800

Lambda0(nm)

ns

TTS=0psTTS=35psTTS=50psTTS=75psTTS=100ps

Taking longer ⇒better resolution (in general), but dominated with finite TTS.


If TTS =0Taking longer ⇒

Sqrt(Npe) decreases

T/(t) increases faster than decrease of sqrt(Npe)

⇒Separation becomes better TOP Separation: L=0.8m, 45deg, 3.5GeV/ c

Bandwidth: +-100nm, TTS=0ps

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

300 350 400 450 500 550 600 650 700 750 800

lambda0 (nm)

Val

ue

DT/ sigtsqrt(Npe)S


But with finite TTS (L16~75ps)Taking longer ⇒

T/(t) start to saturate (at some point) because of TTS

⇒Separation takes the maximum, and then fall with sqrt(Npe)

TOP Separation: L=0.8m, 45deg, 3.5GeV/ cBandwidth: +-100nm, TTS=75ps

0.0

2.0

4.0

6.0

8.0

10.0

12.0

300 350 400 450 500 550 600 650 700 750 800

lambda0 (nm)

Val

ue

DT/ sigtsqrt(Npe)S


With the best TTS (MCP~35ps)Taking longer ⇒

Makes sense(saturation by TTS starts at longer )

Very good separation !2.3 w/ TTS=75ps/0=400nm ⇒4.3 w/ TTS=35ps/0=600nm


0.0

2.0

4.0

6.0

8.0

10.0

12.0

300 350 400 450 500 550 600 650 700 750 800

lambda0 (nm)

Val

ue

DT/ sigtsqrt(Npe)S


With TTS=50ps (Si-PM)The maximum is around 500nm with constant QE=20%.

But, if QE×geom) = 35% achieved, it will lift up the separation at around 600nm.


0.0

2.0

4.0

6.0

8.0

10.0

12.0

300 350 400 450 500 550 600 650 700 750 800

lambda0 (nm)

Val

ue

DT/ sigtsqrt(Npe)S


How about narrower bandwidth (±50ps)?For MCP(TTS=35ps), good separation is achieved at around 450~500nm (green extended bialkari+filter ?).

For Si-PM, it is not good idea.


0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

300 350 400 450 500 550 600 650 700 750 800

lambda0 (nm)

Value

DT/ sigtsqrt(Npe)S


0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

300 350 400 450 500 550 600 650 700 750 800

lambda0 (nm)

Value

DT/ sigtsqrt(Npe)S


Worth for ConsiderationLinear array multianode MCP-PMT w/

Good packing factor (=> next slide)

GaAs(P) or Green extended bialkari

or any photocathode in this range

Good QE is necessary to compensate the geometrical loss in collection eff.

Reasonable cost

Si-PM w/Good geometrical efficiency

Low enough noise rate

Reasonable cost

Questions to HPK !!!

Effective area ~(70 － 80)% (×collection eff.)Very fast, good timing resolution < 50psOperate in magnetic fieldA solution complemetary to

HPD/HAPD (Aerogel-RICH)Finemesh PMT (TOP)

Fundamental (technical) issues must be studies before starting the test production.

MCP indium shieldingMCP mounting etc.

We start from preliminary investigation for these issues.

Flat-Panel MCP-PMT

50 ｍｍ

40~45 ｍｍ50 ｍ

ｍ

40~45 ｍｍ


SummaryPhotodetection is the present critical issue.

First, establish L24-Reproduce the result in the paper.

Assess and solve cross talk problem (if significant).

Packaging to maximize the effective area.

⇒ Experimental verification of performance (no assumption).

In parallel, consider/develop alternatives sensors

Expected improvement factor from the above achieved point.


Summary (cont’d)We want to give statements;

1. “The detector will work with such performance with the present technology.” (no matter how good/bad the performance is).

2. “The performance will be improved by factor of … with technology under development.”

Indeed, this was the case for the present Belle-ACC development.Remember Npe = (was)

~1 in early cosmic tests.~5 with beams right after I was appointed at KEK.>10 approved for construction>15 for the final prototype

This is the way to improve a new detector !


Summary (cont’d)High resolution (pipe-line) time read-out

TS (G.Varner)TMC (Y.Arai) Connection to other groups (BaBar, ALICE, BES-III, …)

GeometryButterfly-TOP

• Easy to analyze, hard to install in Belle geometry?

Bar-TOP• Easy to install, hard to reconstruct hits.

Optimization of bar width, thickness etc.

BackgroundStart discussing with Yamamoto-san etc.-ray effects

Geant simulation

toru iijima / nagoya top: what has to be done (before decision) bar quality seems to be...

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