2009 Olin Student Projects

2009 Olin Student Projects

Keith Gendreau

[email protected]

301-286-6188

Phil Deines-Jones

[email protected]

301-286-6884

Jeff Livas

[email protected]

301-286-7289

mailto:[email protected]





2009 Student Projects with contacts

• Continuation of MCA– Keith Gendreau

• XACT Sounding Rocket Optical Bench Alignment System– Keith Gendreau, Phil Deines-Jones

• UV flux monitor– Keith Gendreau

• Super Webcam microscope– Jeff Livas

• USB Bit Error Rate Measuring Tool– Jeff Livas

Continuation of MCA project from 2008

• In 2008, I asked the Olin students to make a “$25 MCA” to measure pulseheights and record times of X-ray events from a detector.

• System nearly worked, but not quite…

A PIC Microcontroller Based Pulse Detection and

Measurement System

Take an input analog signal, look for pulses above a threshold, detect the peak voltage of each pulse, digitize the peak voltage, write to a file the pulse time and peak pulse height, continue….

Build on last year’s “Flux Meter”, if possible.

X-ray Detection and Pulses

X-ray Detector Amplifier

Vsignal

X-ray photons

X-rays pack a lot of energy. X-ray detectors see individual X-ray photons. If the detectors and electronics are good enough, they can determine the energy of the photon.

Science is to be gained by knowing the energy of the photons and when they arrived.

Pulses on an analog signal (from an X-ray detector)

V

ttpulse

vpulse

Pulse widths: ~25 ns- 2µsec

V

t

vthresh

Pulse#1 Pulse#2 Pulse#3

Vpulse is proportionalto Energy of photon

Noise pulses?

Desired Layout: Top view

Olin Pulse Height Box

Analog signalFrom X-ray DetectorOn a BNCConnector

Knob for Additional gain

Knob for Lower VoltageThreshold

USB Output

ComputerWith Olin Software

To display/saveEvents

Any type of computer, PC or Mac(I prefer Mac, but whatever is doable)

Requirements

• Must handle pulses ranging from ~< 100 nsec to ~ 100 microsec wide– Loosen requirement: Require 1-50 microseconds

with a goal of 100 nsec to 100 microseconds

• Goal of achieving ~106 counts per second (typically, it is much less than this, I’d be happy with ~104 cps)– Loosen requirement to ~1000 cps with a goal of 105

cps

• Should be able to handle pulseheights ranging from ~0 to 10 volts (positive).

Output Desires

• ASCII file with time and pulseheight for each event above threshold• Plot with histogram of pulseheights • Flux vs time (like on the flux meter)• Be creative.• TCP/IP port?

• eg, The computer reading the instrument can make the data available as a server to others as client computers via a TCP/IP Sockets protocol• Would be an extremely useful feature for beamline work.

For 2009

• I will send you home with a detector

• We could not get the software to work from last year.

• Last year’s board broke at the USB connection and we now have a flaky USB board on one of our computers… (QA)

Project #2, XACT Optical Bench Alignment

• We are in the initial phases of designing and building a suborbital rocket payload to do astrophysics

• Science is realized when optics can direct photons to detectors about 3 meters away.

• An optical bench separates the optics and the detectors…– Can we measure the relative alignment of these?

• Tip/Tilt and X/Y offsets

XACT Payload and Rocket

X-ray Concentrators & Star Tracker

Optical Bench

X-ray Polarimeters, Electronics, & MXS

Overall Payload Length: 3.26 mPayload Diameter: 52 cm*

Payload Mass: 80.2 kg (include ST)A 1st approximation of complete XACT rocket

Black Brant VC

Terrier Mk70

Aft Cone & Door

Nose Cone & Recovery System

Telemetry and ACSSystems

Alignment

• X-ray optics must not shift laterally more than ~1 mm from a line connecting the source to the detector– Measure to 0.1 mm

• Optics must not tilt relative to detector more than ~ 2 arcminutes– Measure to 1/5

arcminute

Laser

BeamSplittersPosition Sensitive Photodiodes

Laser

BeamSplittersPosition Sensitive Photodiodes

Lateral Shift Part

Tilt Part

Components

• Position Sensitive Photodiodes– Produces analog voltage proportional to position of

light centroid– Made by Pacific Silicon Sensor

• Laser• Mirrors• Beamsplitters• “the Smarts”

– Combines the outputs of the photodiodes and puts out 4 types of data: X and Y offset, Tip and Tilt angle

QuickTime™ and a decompressor

are needed to see this picture.

I’ll give you these as well as a laser and some optics…

Olin Student Job for XACT Alignment System

• Design full system- including the “smarts”

• Build a prototype system using two optical benches separated by ~ 3 meters

• Test

• Document

Olin student Project #4: UV flux monitor

• Our new modulated X-ray source uses UV light to generate photoelectrons which are accelerated into high voltage targets to make X-rays

• We like to have absolute control of the X-ray flux, which is driven by absolute control of the UV light (from LEDs)

• We have found some evidence of UV LED instability

• Need a way to monitor UV flux and record it on a computer with time stamps.

Vacuum Flange

Electron Target

Photocathode

LED: Modulate This tomodulate the x-rays.

OpticalPhotons

X-ray Photons

Photoelectrons

10 keV or more

•Characteristics:

• Rugged- no moving parts or fragile filaments- perfect for space flight.

• Modulates x-rays at same rate that one can modulate an LED

• Major NASA Uses:

•Timing Calibration

•A “flagged” in-flight Gain Calibration Source: Have calibration photons only when you want them and increase your sensitivity by reducing the background associated with the calibration photons

The World’s First Fully Controllable Modulated X-ray Source

Unpolarized MXS Prototype for XACT

UV LEDs

HV FEED- THROUGH

QUARTZ WINDOWS (2)

BE WINDOW



~3 days

Electronics with a UV

photodiode (Mouser has several) and circuit to read

it.

Computer which reads and records

data at regular intervals, or at

times when there is a change.

USB

Objectives for Olin Summer UV Flux monitor Project 2009

• Design and build UV Photodiode circuit

• Build a USB interface

• Write software to record data- perhaps triggered by changes in flux

• Calibrate

Olin student Project: $75 Diffraction-limited microscope

webcam

Single lens

Protective tube

“Simple” Microscope

Webcam: pixel size will limit resolution

Add on another Single lensAnd maybe a support tube

“Compound” Microscope: 2 lenses



• Requirements– Approximately 1 micron resolution (~ 2 !)– Reasonable working distance (~ 10 mm)– Built-in calibration capability?


• Tasks– Figure out single lens focal length– Work out required additional lens– Figure best-possible resolution based on

number of pixels, diffraction, etc– Prove it!

• http://en.wikipedia.org/wiki/1951_USAF_Resolution_Test_Chart

• Out of the box:– Roughly 5 mils is easy– 1.3 Mpixel is 640 x 480 color

• 640 x 480 x 4 = 1.3 Mpixels

• From picture– guess 127 um is 1/10 x 480 = 48 pixels, or 2.6

pixels/micron (color)


Shim stock on edge

0.005” = 127 m

Olin Objectives for Microscope Project:

• Design add on optic for current microscope

• Build and Test

• Update software to transfer calibration to images

Olin student Project: Bit Error Rate (BER) Test System

• Idea: quantitatively measure the performance of a comm link

• Concept: Go digital!– Send a pattern out with the transmitter– At the receiver, recover the pattern

• May be difficult to find if many errors• Overall time shift not important• May be inverted

– Count the errors• Accumulate statistics on type of error, etc


0110010111

Transmitter

Noise

Receiver

Clock

0110010101

Clock recovery

1 0

1 Error

0 Error

TxRx



– Count the errors• Accumulate statistics on type of error

Noisy Channel

Error types


0110010111

Transmitter

Noise

Receiver

Clock

0110010101

Clock recovery

1 0

1 Error

0 Error

TxRx




Noisy Channel

Error types

Block Diagram

Computer with Olin Student software that prepares the

test pattern for transmission, issues

transmit command, and compares received to transmitted. Finally

produces a BER figure

USB

Olin Electronics box that

produces test pattern and

sends it out a BNC. Box also has a BNC for

the receive end

BNC out

BNC In

“comm Link”


• Tasks– Choose test patterns, build generator– Develop clock recovery (PLL)– Develop “pattern recognition”

• Cross-correlation based often best

– Time shift by bits to find best fit– Accumulate error statistics– BER = number of errors/total bits sent

Projects we probably wont do this year

“i-Heliograph”

• Can we make a low power data transmitter to send “lots” of data from the moon to the earth using a 19th century idea enhanced with 21st century technology?

• How does such a system compare to laser communication?





Replace this guy with a high speed optical modulator and an ethernet port.

Replace this guy with a avalanche photodiode and an ethernet port..

Replacing the guy wiggling the mirror

• Voltage Controlled LCD displays (KHz Speeds?)

• Acoustic Optical Modulators (speeds up to 100 MHz)

Replacing the guy using his eye to see the signal on the

receive end• Avalanche Photo diodes

There should be a power savings compared to Laser

Comm• Lasers are ~10% efficient on producing

optical output from electricity it gathers from ~25% efficient solar cells.– Total efficiency from sun = 0.25 * 0.1 =

2.5%

• Mirrors are ~90% reflective

Other factors in comparison

• Mass to moon– Do solar cells and power system with Laser

weigh more than a mirror and heliostat?

• Reliability– Solar panels, motors, AOMs…– Is dust an issue?

2009 Olin Job

• Build a Heliostat to capture the sun• Pipe the light from the Heliostat through either

an accoustic optical modulator or a LCD retarder

• Build a simple pulse frequency modulator to drive the AOM or LCD retarder

• Build a demodulator to read the output of an APD

• Predict performance and compare to Laser Comm.

GSFC will provide

• A telescope base to make a heliostat• An AOM to modulate light• A Circuit design to produce a FM Pulse

train• A Telescope for the receive end• An APD (maybe dual use the one for

the MCA project)• The demodulator design.

Olin student Project: Laser Ranging System

Lunar Laser Ranging BackgroundLunar Laser Ranging Background• First suggested by R. H. Dicke in early 1950s.

• MIT and soviet Union bounced laser light off lunar surface in 1960s.

• Retroreflectors proposed for Surveyor missions but not flown.

• Retroreflectors flown on 3 Apollo missions.

Science of LLRScience of LLR

• Lunar ephemerides are a product of the LLR analysis used by current and future spacecraft missions.

– Lunar ranging has greatly improved knowledge of the Moon's orbit, enough to permit accurate analyses of solar eclipses as far back as 1400 B.C.

• Gravitational physics: – Tests of the Equivalence principle – Accurate determination of the PPN parameter β,γ, – Limits on the time variation of the gravitational constant G,– Relativistic precession of lunar orbit (geodetic precession).

• Lunar Science:– Lunar tides– Interior structure (fluid core)

Optical CommunicationsOptical Communications• With an optical link it is natural to use it for communications in addition to ranging.

• Potentially higher capacity over large distances than RF communications.

• Several methods currently under development at GSFC.

Parameter Downlink

Uplink

Wavelength (µm) 1.55 0.775Data Rate (Mbps) 900 550Tx aperture (cm) 5.00 40.00Rx aperture (cm) 202.50 5.00Code Rate 0.80 0.80receiver sensitivity (photons/bit) 100 100

BER 1.50E-031.50E-

03Output power (W) 1 8Transmitter losses (dB) -3.8 -3.8Net prop loss (dB) -80.78 -88.85Receiver losses (dB) 2 2Net Rx power (dBm) -52.58 -51.62Net Margin (dB) 0.86 0.95

Other applicationsOther applications• Collision avoidance

• Robotics

• Delay estimation

Olin student Project: Ranging System

0110010111

Transmitter

Noise

Receiver

Clock

0110010101

Clock recovery

1 0

1 Error

0 Error

TxRx

• Concept: Nominally same as for BER– Send a pattern out with the transmitter– At the receiver, recover the pattern

• May be difficult to find if many errors• BUT - Overall time shift IS important• May be inverted


Olin student Project: Ranging System

• Tasks– Choose test patterns, build generator– Develop clock recovery (PLL)– Develop “pattern recognition”

• Cross-correlation based often best

– Time shift by bits to find best fit– Measure time shift to get range

Documents

2009 Olin Student Projects