Status of RICH mechanical design at PNPI

E.Vznuzdaev for PNPI group:

V.Dobyrn, A.Khanzadeev, E.Kormin, V.Lebedev, N.Miftakhov,

V.Polyakov, V.Samsonov, O.Tarasenkova, V.Tolchin, E.Vznuzdaev

Previous meeting - ”point of departure”

RICH mirror layout

Tasks for the current stage Design of the mirror mount for thin

(3mm) trapezoid mirrors with dimensions of 400mmx400mm

Development the test-bench for optical measurements to study the mount influence on the mirror optical quality and to determine the mirror adjustment procedure

Basement of the mount design for thin mirrors

Common considerations:- mirror unit mirror mount mirror truss- mirror unit + mirror mount = one thing (mirror module)- mirror mount includes adjustment mechanics

Problem:- this is a problem to connect a thin spherical mirror unit with adjustment mechanics immediately (fragility) strong requirement to safe handling Decision:-one of the way to implement such a connection is to do this with an intermediate flat panel

Sphere-plane transition

5-point sphere-plane transition is proposed

CFC tubes for transition (Exel Industry)

Thin and rigid sandwich with small density supposed to be used as flat panel

Sandwich (can be provided by Subatech, Nant): core - 8 mm Nomex honeycomb with density 1347g/m2; skins are made from 2x0.1 mm thick CFC with high tensile modulus 314 Gpa (LHC, ALICE project, muon chambers) 3-D design of the transition

Assembling of the sphere-plane transition

Assembling sequence: Arrangement of the

mirror with safety film on the mould with the same spherical surface

Setting sandwich panel immovable above the mirror

Inserting tubes into the holes

Gluing bottom and top ends of the tubes with mirror and sandwich

3-D model of the mirror/mount prototype

The triangular mounting arrangement allows to adjust the mirror by rotation of three mounting screws, rigidly attached to the sandwich

To avoid the deformation of the mirror panels:

a ball joint is applied for the one of the mounting point on the mirror;

balls in slots is used for the other two mounting points

Gravity deformation of the mirror: vertical position

FEM calculations:Maximum deviation from spherical shape~ 0.2 microns

Gravity deformation of the mirror: inclined positions

mirror slope=+20°,max. deviation<2microns

mirror slope=-20°,max. deviation<2microns

FEM calculations

Test-bench for optical measurements

Purpose – study of optical characteristicsfor mirror/mount prototype

Horizontal (+/- 45°) and vertical (+10/-25°) rotation of the mirrors

Optical measurements for different angle positions of the mirrors

Time stability study for mirror mount Measurements of regulation

dependencies for adjustment mechanics Study of the adjustment procedure

Optical quality measurements

Conventional procedure of the optical quality (Do) measurements

Mount influence on Do value Point source: red He-Ne laser with

diaphragm CCD: mat screen and web-camera

with USB output

■ Current status – creation of the measurement procedure, hardware and software development using flat mirror as reflective surface with divergent laser beam

Laser beam reflection (~4%) from two sides of the light splitter to obtain the reference point for the test -bench

Test-bench tuning (hardware and software) with flat mirror

Scanning of the spherical mirror surface with He-Ne red laser beam;

Time stability study for mirror/mount prototype

Using light splitter

Experimental setup with light splitter

Next steps

Mirror/mount prototype construction Tool and equipment development for prototype

assembling Choice and acquisition of materials for prototype

construction Prototype assembling

Optical test measurements Optical quality Time stability Development of the adjustment procedure Adjustment parameters measurements

SPARE

2x2 mirror unit configuration

Dimension of the mirror unit: 200mm x 200mm

Compound mirror moduleconsists of 4-th units

Precondition to use such a design is case of insufficient optical quality for 400mm x 400mm mirror unit

Using of developed sphere-plane transition technology of assembling

View of mirror support section

Sequence of the RICH mechanics design process

Simulation Preparation of design specifications Conceptual design(3-D modeling, FEM

calculations) Prototyping and testing Simulation Improvement of design Engineering design