2009 Olin Student Projects Keith Gendreau Phil Deines-Jones Jeff Livas

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 DetectorAmplifier V signal 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 t t pulse v pulse Pulse widths: ~25 ns- 2µsec V t v thresh Pulse#1Pulse#2 Pulse#3 V pulse is proportional to Energy of photon Noise pulses?

Desired Layout: Top view Olin Pulse Height Box Analog signal From X-ray Detector On a BNC Connector Knob for Additional gain Knob for Lower Voltage Threshold USB Output Computer With Olin Software To display/save Events 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 ~10 6 counts per second (typically, it is much less than this, I’d be happy with ~10 4 cps) –Loosen requirement to ~1000 cps with a goal of 10 5 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 m Payload 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 ACS Systems

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 BeamSplitters Position Sensitive Photodiodes

Laser BeamSplitters Position 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

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.

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 lens And maybe a support tube “Compound” Microscope: 2 lenses Olin student Project: $75 Diffraction-limited microscope

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

Olin student Project: $75 Diffraction-limited microscope 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!

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) Olin student Project: $75 Diffraction-limited microscope 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

Olin student Project: Bit Error Rate (BER) Test System Transmitter Noise  Receiver Clock Clock recovery Error Tx Rx 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 Noisy Channel Error types

Olin student Project: Bit Error Rate (BER) Test System Transmitter Noise  Receiver Clock Clock recovery Error Tx Rx 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 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”

Olin student Project: Bit Error Rate (BER) Test 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 –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 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 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 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. ParameterDownli nk Upli nk Wavelength (µm) Data Rate (Mbps) Tx aperture (cm) Rx aperture (cm) Code Rate0.80 receiver sensitivity (photons/bit)100 BER1.50E-03 Output power (W)18 Transmitter losses (dB)-3.8 Net prop loss (dB) Receiver losses (dB)22 Net Rx power (dBm) Net Margin (dB)

Other applications Collision avoidance Robotics Delay estimation

Olin student Project: Ranging System Transmitter Noise  Receiver Clock Clock recovery Error Tx Rx 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 –Count the errors Accumulate statistics on type of error

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