# Presentation: 189600

## BNL Review		February 19th, 2007

**1**

**MECHANICAL DESIGN AND STUDIES FOR THE *****FVTX***** DETECTOR, ALONG WITH ITS INTEGRATION AS A PART OF THE *****VTX***** **

**WALTER SONDHEIM, ****LANL ****MECHANICAL SYSTEMS ENGINEER FOR THE *****VTX***** & *****FVTX***

## BNL Review		February 19th, 2007

**Outline****:**
**Mechanical Specifications and Requirements**
**Baseline  Design**
**Initial Material Selection**
***HYTEC***** FEA Analysis**
**Wedge/Half-disk Assembly Scenario**
**Mechanical Integration with the VTX System**

**2**

## BNL Review		February 19th, 2007

**3**

**Future home for the *****VTX***** and *****FVTX***** detectors: Muon arm acceptance: 12 – 35 degrees**

***As they***** *****say in Real Estate, “******location, location, location******”.***

## BNL Review		February 19th, 2007

**4**

**Basic components of the FVTX 15 degree wedge detector:**

**Silicon Sensor (1)**

**PHX readout chips (26)**

**HDI**

**Thermal back-plane, behind HDI**

**35.mm**

**Readout connectors (2)**

**Beam Axis**

## BNL Review		February 19th, 2007

**5**

**Each large detector panel would consists of 30 - 15 degree wedges, mounted to a honeycomb core panel front-to-back, offset by 7.5 degrees in *****phi.***

## BNL Review		February 19th,2007

**Mechanical Specifications and other Requirements****:**
**The FVTX is expected to receive *****20 kRads***** exposure per year**
**Nominal detector design resolution is ****~*****20. microns***** or better in *****r *****and much larger in *****phi*****.**
**Require that the placement of the silicon sensors on a plane be placed and surveyed to an accuracy of *****10. microns***** in *****x***** and *****y*****.**
**Static distortions of the planes should also be at or below *****10.***** *****microns***** in *****x***** and *****y.***
**Static distortions in *****z*****, or a given sensor being out of plane, should be kept to *****10.microns/tan(35) = 14. microns***** or less. 35 degrees is the maximum acceptance track angle.**
**Stability due to vibration must be kept less than *****10. microns*****.**
**Station to station alignment in the FVTX has a goal of *****75. microns*****, could be as high as *****200. microns*****. Verification with straight-through tracks.**
**Survey installation < *****200. microns*****.**

**6**

## BNL Review		February 19th, 2007

**Baseline Design & Material Choices:**
**The *****FVTX***** detector will consists of 4 planes, each plane is hermetic phi.**
**Each detector panel consists of:**
**One ****structural panel**** consisting of 1/4” thick (6.35mm), 2 lb/ft****3**** aluminum honeycomb; 3/8” (9.5mm) cell size, .0007” (0.018mm) thick film, 5056 aluminum. Bonded using heat activated epoxy tape. Outer skins 10 mil (.25mm) thick, quasi isotropic GFRP (glass fiber reinforced polymer);**
**4 plies [0/45/90/-45], pre-preg unidirectional tape**
**M55J graphite fiber, 954-3 cyanate ester matrix, 60% FVF**
**Each panel 7.1 mm thick, RL 0.376%**
**Thermal back-plane**
**0.25mm TPG core**
**0.13mm GFRP face sheets, 2 layers M55J/954-3, [0/90]**
**HDI**
**176 micron thick**
**4 copper planes (ground, power, 2ea. Signal), 5 Kapton films, 8 glue layers**
**Mini-strip Silicon Sensor**
**300 micron thick**
**Bonds**
**Rigid bonds – unloaded, exception sensor to HDI thermally conductive epoxy**

**7**

## Radiation Length of Baseline Design

**Panel total %RL**
**Worst case = 2.16%RL**
**Using average of ROC+bond and SSD+bond**
**Area averaged = 1.84%RL**
**Detector and HDI account for >40% of total (area averaged)**

- Stackup of RL contributions for 1⁄2 FVTX panel
- (from mid-plane to detectors)

- One or the other, not both

**8**

## HDI Baseline

**From Mark Prokop, 02/05/07**

- 100% coverage

- 25% coverage

- 25% coverage

- 100% coverage

- (?) My calculations give 0.206%RL 

**9**

## HDI Baseline – Material Properties

**10**

## BNL Review		February 19th, 2007

**11**

**Proposed interconnect between the HDI and the ROC, which is mounted in the “Big Wheel” will be the Hirose Electric Company DF-18 connector 100 pin connector. These connectors are similar to the ones being proposed for the VTX pixel bus.**

## BNL Review		February 10th, 2007

**12**

**Baseline design for the ****VTX**** and ****FVTX**** detectors;**

**FVTX****-ROC**

**FVTX**** - 4 detector planes each end**

**Each big wheel will have 5 planes of read-out electronics, with one cooling plate for each plane**

## BNL Review  	February 19th, 2007

**13**

**FVTX support cage: 4 stations:**

**Support cage is a similar structure to the detector support panels – aluminum honeycomb with GFRP skins. Each half cage meshes to the mating half cage to help relieve “drum-head” effects. Each station has 15 degree sensor panels mounted on both sides – offset in *****phi***** by 7.5 degrees.**

**FVTX mounting tabs**

## BNL Review		February 19th, 2007

**14**

**sensor**

**HDI**

**thermal plane**

**Cooling tube**

**Detail view of FVTX support cage with panels:**

**PHX chips**

**Support cage – al. honeycomb with graphite fiber reinforced polymer (GFRP) face sheets**

## BNL Review		February 19th, 2007

**15**

**HYTEC has integrated the proposed HDI to the “wedge”, that will work for all wedges.**

**Note that the current model allows for a mech mounting for each wedge using pins and screws**

## HYTEC - THERMAL FEA:

**Model represents old (worst case) baseline**
**28 35mm IR**
**ROC’s per SSD**
**About 8% more heat, and 8% longer radial heat transfer path**
**Readout chip heat generation:**
**Waste heat per channel: 100 ********W**
**Channels per chip: 128**
**One chip volume : 0.009×0.0015×0.0003=4.05×10****-9****m****3**
**Heat generation per chip: 0.0128/4.05×10****-9****=3.16049×10****6****W/m****3**
**Backplane layup:**
**TPG core, 0.246mm thick**
**Symmetric [0°/90°] Gr/CyE face sheets (each layer 0.0635mm thick)**
**Total thickness: 0.5mm**
**Effective backplane thermal conductivities (estimated):**
**K****x****=755.83 W/m.K**
**K****y****=755.83 W/m.K**
**K****z****=1.88 W/m.K**
**Edge cooling at 0°C (arbitrary temperature at this point)**
**Backplane nodes on the outer edge are kept at 0°C**
**Additional temp. drop from backplane OD to fluid bulk temperature **_**not**_** yet included**
**HT coefficient + TTT drops in tube wall, face sheets, bonds, etc.**

**16**

## 3-D FE Model

**Mesh:**
**158,225 nodes and 270,220 elements**
**3-D solid elements for: backplane, glues, Kapton bus, readout chips, and strip detector**
**Loads:**
**Volumetric heat generation in the readout chips**
**Edge cooling at 0°C**

**17**

## 3-D Temperature Contour

**3-D Temperature Contour**

**With conductive epoxy (1.5W/mK) between ROC & HDI**
**Temperature in oC**
**Assuming outer edge of TPG held at 0oC**
**Warmest ROC at 2.55oC**
**2.5oC <<< 50oC**
**Backplane much more conductive than required**

**18**

## Total Heat Flux

- Kapton Bus

- Backplane

- Non-conductive Epoxy

**19**

## Total Heat Flux

- Readout Chips

- Conductive Epoxy

**20**

## Concluding Remarks  on Thermal FEA

**Baseline design is simple and modular, but not optimal**
**Duplicate functions: backplane + panel face sheets**
**Lots of bonds**
**Expensive & problematic materials (TPG) may not be needed**
**Good enough?**
**Easily meets temperature requirements with edge cooling alone? (TBC)**
**ROC temperature < 2.6oC**
**Not accounting for convection into N****2****, i.e. conservative**
**Using TPG (~750 W/mK) may be a waste**
**Try CC (~240 W/mK, or 3× lower) or even GFRP (~75 W/mK, 10× lower)?**
**No need for thermal vias through HDI**
**Future work**
**Finalize specification document?**
**Extend model to mid-plane (represent panel)**
**More detailed representation of cooling channel**
**Explore other back-plane material options**
**Evaluate stresses and select adhesives**
**Evaluate effect of convective HT (negligible?)**
**Cooling & flow calculations**
**Iterate!**

**21**

**Comments by Eric Ponslet from**** *****HYTEC***

## HYTEC - MECHANICAL FEA:

**System level FEA Summary PHENIX VTX & FVTX**

**22**

## FVTX Disks

- Honeycomb core sandwich panel are used for the disks
- Symmetric quasi-isotropic [-45/90/45/0]  M55J/954-3 facesheets (ti=0.0635mm)
- Aluminum honeycomb core (32.0Kg/m3, t=6.35mm)
- Total thickness: 6.858mm
- Attached electronics are modeled as non-structural mass (~4.255 Kg/m2)
- Approximate mass of half disk: 0.234Kg (everything included)

**23**

## FVTX Cage

- Honeycomb Al Core with Gr/E face sheets is used for the FVTX cage
- Cutout design is a baseline design
- Disks are attached to the cage at three tabs in the current design
- Each half of the cage is connected to the space frame at two tabs

**24**

## FVTX Stand Alone Modal Analysis

- Assumed to be fixed at the support tabs
- First mode: 83.9 Hz (over predicted because of the fixed support assumption)
- Even higher than the “utopic” frequency of 75Hz!
- Potentially a less stiff structure could be used
- Adding additional supports at the back of the cage would improve the frequency
- Connecting half disks for each layer using pins and/or clips

**25**

## VTX & FVTX Assembly

- First Mode: 38Hz (derived by the barrel mounts)
- Can be improved by:
- Connecting layer 4 barrel mounts to the space frame at 3 points rather than 2.
- Increasing the thickness of the HC Al Core for the barrel mounts
- Increasing the width of the barrel mounts at the base.

**26**

## FVTX Deformation Summary

**FVTX Deformation Summary**

**FVTX Disk deformation summary**

- Note: detector payload modeled as mass only

**27**

## FVTX Stand Alone 

**28**

## System Level FEM Model

- System level model as of 10/13/2006 (cf. HTN-111006-0002)
- First Mode: 24.5Hz (Drum Head mode)

**29**

## Barrel Mount Bracings

- Bracings (baseline HC core sandwich panels) are added to improve the stiffness
- First mode increases by 55% to 38Hz

**30**

## VTX Deformation Summary

**Staves deformation summary with barrel mount bracings installed**
**Max deflection is reduced by 4%**
**Staves deformation summary with barrel mount bracings and FVTX installed**

**32**

## PHENIX Assembly on Support Stand

- System level model with Support Stands/Rails
- 118,814 Nodes
- 147,536 Elements
- 712,884 degrees of freedom
- First mode: 24Hz
- First mode is driven by the support rails

## VTX (No Bracings)

- First Mode: 24Hz

**33**

## VTX with Bracings

- First Mode: 38Hz

**34**

## VTX+Bracing+FVTX

- First Mode: 38Hz

**35**

## PHENIX Assembly on Support Stands

- First Mode: 24Hz

**36**

## BNL Review		February 19th, 2007

**Assembly steps****:**
**15 degree wedge**** –**
**Mount HDI to the Graphite thermal plane;**
**Using vacuum fixtures**
**The HDI Kapton must be mounted as flat as possible, surfaces must be kept clean prior to bonding – suggest plasma cleaning.**
**Install surface mount components on to the HDI; **
**Be certain that all solder “grunge” has been removed prior to the attachment of the silicon sensor.**
**Silcon sensor is attached to the HDI;**
**Using vacuum fixtures**
**A suggested bonding agent is 3M 9882 thermally conductive transfer tape (CMS), 50. microns thick.**
**http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs666yazCOrrrrQ-**
**Make wire-bond connections and encapsulate attachment points**
**Characterize completed 15 degree wedge sensor assembly using a CMM (Coordinate Measurement Machine).**
**Mount 15 degree wedges to support panel**
**Again characterize assemby using CMM**

**37**

## BNL Review		February 19th, 2007

**38**

**SIDET lab optical CMM machine, optical resolution in x-y; 3.1 microns uncertainty**

## BNL Review		February 19th, 2007

**39**

**SIDET example of touch probe stations, resolution 3.5 micron uncertainty**

## FVTX integration with VTX

**40**

**FVTX mounts to the VTX space frame off of tabs at the front of support cage. **
**We plan to improve the stabilization of this support cage by adding a “diving board” to the VTX space frame that will pick up an additional support point on the FVTX cage in Z.**