Status of the Genova activity on a direction-

sensitive optical module toward the KM3 detector

M.Taiuti WP3PYLOS 16/4/2007

Guidelines

We planned the construction of 2 directional optical module to be deployed together with the NEMO-Fase2 tower in Capo Passero

Integration to be completed by may 2008

Compatibility with the mechanical structure of the NEMO-Fase2 tower

Compatibility with the electronics of the NEMO-Fase2 tower

Basic Requirements

A direction-sensitive optical module requires:

A. A position sensitive photo-detector

B. A light collimation system

C. A dedicated electronics

The Optical Module Conceptual Design

Highly reflecting mirros (by 3M)

Highly reflecting mirros (by 3M)

Plexiglas (90 mm)

Plexiglas (90 mm)

PMT 10”PMT 10”

Sphere 17”

Sphere 17”

Mu-metalMu-metal

Optical Gel (7mm)

Optical Gel (7mm)

PMT FrameTo be optimized

PMT FrameTo be optimized

The Hamamatsu Prototypes

2 prototypes manufactured and received in Catania in May

Same shape as 10” standard PMT

Very large photocathode area

No data-sheet presently available. Hamamatsu is waiting for the publication of out tests

The Hamamatsu Prototype Properties

Preliminary test performed by Hamamatsu

Results confirmed in Catania

Good response• Gain > 5 107 (> 5 107)• PtoV > 2.5 (> 2)• TTS < 5 ns (< 3)

Uniformity

Test in Catania

Test in Catania

preliminary

preliminary

Test in Catania

Preliminary tests performed with diffuse light source

This week new tests will begin with laser light source, including:• Cathode uniformity• Anode cross-talk• Single photon peak• Timing• Linearity

The Light Collimator

Spherical geometry allows an easy solution to the problem of efficiently collect the Cherenkov light with three plane mirrors forming 90° intersections

Volume between mirrors must be filled with transparent media to match the refraction indexes (chosen low cost solution: Plexiglas)

R

x

R

x

Œ Ž

Test on Reflectance

Reflectance

0

100

200

300

400

500

600

470 480 490 500 510 520

Wavelenght (nm)

Ref

lect

ed P

ow

er (

m W)

3M

3M Tekno

HiFi

Domopack

plex

igla

s

photodiode

laser

Power supply

ISEG PHQ-5912 board has been analyzed and evaluated. A new prototype is in advanced design phase. Design objectives: low power, good performances,

reliability, compactness. Main features:

• Positive voltage up to 2000 V• Independent regulation of cathode to first dynode

and first dynode to anodes voltages• Single supply (+5 V)• Remote On-Off switching• Voltages setting using local DACs or analog values• Voltages and current monitoring using local ADC• On board thermometer

A working prototype is expected to be ready by June 2007

Read-out electronics

The information needed are: • the total collected charge • the index of the fired anodes• signal time-evolution

A dedicated electronic board will be designed to provide the analog sum of the 4 anode signals and 4 discriminated digital signals.

The actual NEMO FEM can be used implementing dedicated firmware on it.

The NEMO FEM will provide the discriminator thresholds and the power to this module.

The data payload will contain the digitized data together with the index of the fired anodes.

DAC

DAC

DAC

DAC

S

TO FEM

Time scale

PMT test by May 2007

Light guide construction by May 2007

Mechanical assembly by July 2007

Tests with conventional electronics by December 2007

Read-out electronic board ready by December 2007

Final assembly and test by June 2008