Thin ladder development Status of ladder development for the thin ladderfest

Targets Aiming for 0.1 % X 0 Uniformity over full length of ladder Compatibility with wire and bump bonding Provision for optical survey Robust

The story so far… Have followed up three different approaches –Unsupported, ladder made purely from thinned silicon and tensioned. –Fully supported, ladder placed on a self supporting substrate. –Semi-supported, ladder placed on a supporting substrate but tensioning still required.

Unsupported Ladder Several thin ladders where made and stability found to be good along the length. –Concerns arising are the there is no strength across the width –Studies by Glenn Christian at E2V confirmed fears, but no figures were able to be obtained

Fully Supported ladders Shape of substrate would make it fairly non- uniform, at some angles particles would have to pass through a large amount of material Idea to rigidly fix thin silicon (20 microns thick) to a very rigid support –Support substrate could be hollowed out to make it light weight, ie using a V or Ω beam

Semi-supported Tensioned unsupported ladders have good stability along length –Require a lightweight substrate to reinforce width. Pursed to methods with this in mind –tensioned substrate ladders and Sandwiched ladders Tensioned substrate ladders –Uses a gluing pattern similar to that used in SLD experience A stiff substrate is used such as beryllium or carbon fibre The substrate is strong enough to resist curling across the ladder caused by imbalances from the detector but not strong enough that it is self supporting along the length, hence requires tension. Tension Silicon detector Thin substrate Glue pillar Now know beryllium has to large a difference of coefficient of expansion when compared to silicon, hence a thicker detector than preferred

Sandwiched ladders –Makes the detector into a composite material made from a core surrounded by thin silicon. Core can be made from either a foam or a microstructure. Structure strong enough along width, but would require tensioning. Microstructure sandwich Two thin layers of silicon held apart buy thin silicon walls “grown” onto one of the layer of silicon Silicon detector Plain piece of silicon Foam Sandwich Thin layers of silicon held apart by a foam, ie RVC foam Silicon detector Plain piece of silicon

Material profiles Graph below shows how a ladder of different thicknesses, if it is supported along one of it’s edges, deviates with a known force.

Table of comparison Material X 0 (cm)X/X 0 (%)X/X 0 Thickness (cm) Thickness (um) Thickness (m) Elasti Modulus (Pa) Force (N) Length (m) Width (m) Deflection (m) Deflection (mm) E*X 0 3 (Nm) Beryllium E E E E+10 Carbon fibre E E E E+09 Carbon fibre E E E E+10 Carbon fibre E E E E+10 Carbon foam E E E E+10 Rohacell E E E+10 SiC E E E+08 SiC foam E E E E+10 Silicon E E E+07 Stainless Steel E E E+05 Inputs are: Thickness of material and Elastic modulus