# Presentation: 363168

## The BTeV Pixel Vertex Detector

**Marina Artuso** for the **BTeV pixel group**

- Marina Artuso - Vertex 2001

- 9/25/01

## Characteristics of hadronic b production

- b production angle

- The higher momentum
- b’s are at larger ’s

- b production peaks at large
- angles with large bb correlation

- b production angle

- 

- 

- Marina Artuso - Vertex 2001

- 9/25/01

## The BTeV Detector

- Marina Artuso - Vertex 2001

- 9/25/01

## Why pixel?

- Pixels reduce ambiguity problems with high track density & essential to our detached vertex trigger
- Crucial for accurate decay length measurement
- System in secondary vacuum and pixel planes as close as possible to the beam (6mm)
- Radiation hard
- Low noise

- Marina Artuso - Vertex 2001

- 9/25/01

## Pixel Module

**Pixel Module**

- Hybrid pixel detector
- Low mass substrate (mechanical support - cooling)
- Flex circuit (control signals, data lines, power)

- Marina Artuso - Vertex 2001

- 9/25/01

## Hybrid Silicon pixel devices

- Hybrid Silicon pixel devices

- Independent development and optimizations of readout chip and sensor
- n+ pixels on n-type substrates: inter-pixel insulation technology under investigation
- Bump-bonding of flipped chip: 2 technologies  being considered: Indium (In)  and solder (SnPb)

- 0.25 m rad-hard FPIX2 chip

- Marina Artuso - Vertex 2001

- 9/25/01

## Pixel sensor design

- Now studying:
- Moderated p-spray sensors (from ATLAS)
- 1st iteration of sensor submission of our own design: SINTEF submission with a variety of p-stop designs
- radiation hardness studies just started
- Next spring we will study the performance with a test beam of irradiated and non-irradiated sensors coupled with BTeV front end devices (FPIXn)

- 1 of the SINTEF wafers that we are now characterizing

- Marina Artuso - Vertex 2001

- 9/25/01

## Sensor Development Strategy

- Detailed experimental study of different design options
- In parallel simulation effort of electrostatic properties and charge signal development with ISE-TCAD
- The goal: identify reliable design that will provide the spatial resolution needed over the course of several years ( radiation hardness is important)

- Marina Artuso - Vertex 2001

- 9/25/01

## Wafer level Measurements

- I-V
- C-V
- Effect of temperature, humidity, test signal frequency, size
- Systematic study of factors affecting the measurement precision

- Marina Artuso - Vertex 2001

- 9/25/01

## Examples of I-V and C-V characterization of SINTEF prototypes

- Marina Artuso - Vertex 2001

- 9/25/01

## Breakdown voltage

- Marina Artuso - Vertex 2001

- 9/25/01

## Bump bonding

- Issues
- Comparison of indium (AIT) and solder bump (MCNC) options
- Quality assurance, at production and after burn-in tests
- Effects of thinning front end device wafergoal of 200 m fpix2 thickness
- 8” capability of bump bond vendors

- Marina Artuso - Vertex 2001

- 9/25/01

## First step: studies with dummy detectors

- The strategy: use dummy devices (single flip-chip assemblies of daisy-chained bumps)
- 30 m pitch In bumps – 200 chains of 28-32 bumps
- 50 m pitch solder bumps – 195 chains of  14-16 bumps
- Chains connected with  testing pads at each end: resistance of the chain  bump quality
- Tests performed:
- Thermal cycling (-10 C for 144 hr  100  C  in vacuum for 48 hrs)
- Cs137 gamma source irradiation to 13 MRad

- Marina Artuso - Vertex 2001

- 9/25/01

## Rate of occurrence of problems (per bump)

| problem | Indium bumps | Solder bumps |
| --- | --- | --- |
| A good channel develops high R (5-10 K/bump) in 12 months | 2.1x10-4 | 
4.0x10-4
 |
| A good channel develops high R after cooling | 2.2x10-5
 | 1.4x10-4
 |
| A good channel develops high R after heating | 2.1x10-4
 | 6.3x10-4
 |

- Marina Artuso - Vertex 2001

- 9/25/01

## Radiation effects

- In bumps: almost every  1st channel in group of 4 channels was at high resistance (spurious effect?)
- Solder bumps: Al layer on strips and  pads extensively flaky and bubbly after irradiation (accelerate oxidation?) 6/2280 channels broken.

- Al lines after heavy irradiation

- Marina Artuso - Vertex 2001

- 9/25/01

## Readout electronics: FPIX2

- Low noise
- Low and uniform threshold
- Feedback compensation allows to withstand high Ileak
- 3bit FADC in each cell

- 8 prefpix2 front-end cells

- Test structures

- More on this in Gabriele Chiodini’s talk

- Marina Artuso - Vertex 2001

- 9/25/01

## High density flex circuit development

- 15 HDI delivered from CERN; only 4 without defects
- Preliminary performance assessment very satisfactory  design validation
- We need to do more extensive tests and find commercial vendor for large scale production

- Marina Artuso - Vertex 2001

- 9/25/01

## Performance of the Pixel prototype module 

- 1 FPIX1 chip wire-bonded to HDI module with and without sensor bump bonded.
- Noise and threshold dispersion characterization show no degradation with respect to single chip characterization

- Marina Artuso - Vertex 2001

- 9/25/01

## Performance of the Pixel Prototype Module (in e-)

| Without sensor |  |  |  | With sensor |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| <thr> | thr | <ENC> | ENC | <thr> | thr | <ENC> | ENC |
| 7365 | 356 | 75 | 7 | 7820 | 408 | 94 | 7.5 |
| 6394 | 332 | 78 | 12 | 6529 | 386 | 111 | 11 |
| 5545 | 388 | 79 | 11 | 5500 | 377 | 113 | 13 |
| 4438 | 378 | 78 | 11 | 4410 | 380 | 107 | 15 |
| 3513 | 384 | 79 | 12 | 3338 | 390 | 116 | 20 |
| 2556 | 375 | 77 | 13 | 2289 | 391 | 117 | 21 |

- Threshold scan

- No degradation introduced by HDI or bump bonded sensor

- Marina Artuso - Vertex 2001

- 9/25/01

## Our baseline mechanical support: Fuzzy Carbon Substrate ( with ESLI)

- Light-weight
- Good thermal performance and CTE match to Si
- Problems: fragile, heavy manifold and brittle joint between tube and manifold, difficult to fabricate, sole source
- Back-up involves Be structure but would worse material budget

- Marina Artuso - Vertex 2001

- 9/25/01

## Some prototype devices (ESLI)

- Shingled detector

- Nonporous carbon tubes

**Some prototype devices (ESLI)**

- Heat exchanger test heated up by two aluminum plates

- Marina Artuso - Vertex 2001

- 9/25/01

## System Design Highlights

- Pixel sensor telescope needs to be in a secondary vacuum, separated by the beam primary vacuum only by a thin RF shield & is inside a 1.6 T dipole field
- Must be enclosed in a vacuum vessel
- Materials used must not outgas and must be non-magnetic
- Sensors must retract from their regular position during injection and machine studies (precision positioning/alignment)

- Marina Artuso - Vertex 2001

- 9/25/01

## Pixel detector system

- 30 stations (substrates with embedded cooling channels) with 2 pixel planes per station
- Carbon support frame
- Al RF shield
- Cooling system
- Motor drive to move sensors farther from the beam line during injection and beam studies

- Marina Artuso - Vertex 2001

- 9/25/01

## Pixel Vacuum Vessel

- cables

- Carbon fiber support frame

- Marina Artuso - Vertex 2001

- 9/25/01

## Cable Feed -Through

- Use PCB with connectors as vacuum feedthrough
- Large number of cables/connectors
- Large PCB (17x22”), 6 layers now being designed
- This PCB with connectors will be tested in a vacuum system

- Marina Artuso - Vertex 2001

- 9/25/01

## RF shielding

- Same membrane hopefully serve three purposes:
- RF shielding of the pixel detector
- Vacuum barrier
- Image current
- Evaluation in progress

- Marina Artuso - Vertex 2001

- 9/25/01

## Summary

- Great progress has been achieved in the design of the sensor, front end electronics and module structure of the BTeV pixel detector
- This inner tracking system will be the key element of  the Trigger algorithm that  will enable efficient collection of a variety of beauty decays & provide a superb tool to challenge the Standard Model

- Marina Artuso - Vertex 2001

- 9/25/01