John Hedditch
+1 (617) 230-9534 | Arlington, MA | hedj@hedj.org

Education
The University of Adelaide Adelaide, South Australia
B.Sc (Physics, Honours), Ph.D (Theoretical and Mathematical Physics) 1998 — 2006
- University Medal, 2006.

Work Experience
Chief Scientist April 2019 — Present
President Dec 2025 - Present
SGHP Lawrence, Massachussets

- Management
-- Responsible for entire Technical and Scientific Programme
--- Project Plan
--- Deliverables
--- Hiring
-- Supervision of Senior Physicist
-- Safety responsibility for project
-- Facility specification and design
-- Coordinating assistance from nonscientists during assembly phase

- Plasma Devices
-- One very high density (10^16 cm^-3), cold (sub-eV) helium plasma device
--- 3d printed coil forms and mounting hardware
--- Finite-element optimisation of magnetics and mechanics
--- Entire device including instrumentation fits on a table
--- Fully automated operation
-- One very high power (MW) device
--- 3d printed mounting hardware, optical cages, insulators, etc
--- Fully designed in CAD before contruction
--- Shielded, isolated installation in Shipping Container
--- Fully automated operation

- Software development
-- HPC facility for PIC simulation
-- Agent-based Distributed real-time safety and control system
--- No central controller or message queue: agents broadcast netstring-serialised KV pairs over UDP 
--- Agents only need to know their own name to participate
--- Agents can be transparently moved between machines
--- Console automatically builds proxy objects for discovered agents
--- Native C++ code for custom embedded devices (Arduino, PLC)
--- 200-lines of Python for skeleton agent for 3rd party devices provides heartbeat, help
--- 300 lines of Python for custom repl and script-runner with code-gen based on device capability reporting
--- REPL also provides barrier synchronization, failure callbacks, roll-call, online help, etc.
--- All broadcast messages persisted to database
--- Cryptographic hashing for proof of data integrity

-- Watchdog, Interlock and Testing system based on above
--- Agents send messages directly to other agents; broadcast ensures these are logged
--- Fault injection agents spoof messages to simulate problems

-- SPICE Circuit simulation using ngspice, LTSPICE
--- Transmission lines
--- Instrumentation amplifiers
--- Buffer amplifiers
--- Isolation amplifiers
--- Isolated Power supplies
--- High voltage switches (Avalanche transistor, IGBT, MOSFET-cascade)

-- Fast magnetostatics code
--- Written in Julia to allow easy use of GPU for acceleration
--- Derived new exact form for line-integral of vector potential
--- Allowed fast 3D optimisation of coil forms on slow desktop computer
--- Exports to HDF5 for visualisation using Paraview

-- Monte-Carlo plasma-kinetic energy loss calculation
--- Written in Julia
--- Allows collisional calculations using arbitrary distribution functions
--- Calculation of Bremsstrahlung, collisional heating, Synchrotron Radiation, Recombination loss, etc.

-- Automated control and data acquisition from great variety of instruments
--- Oscilloscopes (Rigol, Siglent, Tektronix) [ VXI ]
--- Signal Generators (In-house, Tektronix, Siglent) [VXI, serial]
--- Xray spectrometers (Ametek) [ Custom protocol ]
--- Mass Spectrometer (Stanford Research Systems) [ Custom protocol ]
--- Vector Network Analyzer (Hewlett Packard) [ GPIB ]
--- CPU Design in Verilog
--- LabJack [ MODBUS ]
--- Controllino PLCs [ Native ]
--- AutomationDirect Click PLCs [ MODBUS ]
--- Optical Spectrometers (Ocean Optics, Stellarnet, LightMachinery) [ Proprietary vendor protocols ]
--- Geiger Counters (SE Intl) [ USB HID ]
--- UPSen [ USB HID ]
--- Lasers [ TCP/IP, vendor protocol ]
--- Cameras ( Canon, Teledyne FLIR, Basler, Logitech ) [USB, GigE]
--- many more

-- Retrofitted live-tool CNC turning center for DNC.
--- Ikegai TUR system originally set up for paper-tape
--- Wired relays parallel to all front-panel switches
--- Wired GPIOs to watch front-panel lights
--- Wrote python code to generate toolpaths, drip-feed G-CODE via HMI
--- Built safety interlock system to prevent unexpected or unsafe operation
--- Enormous improvement in flexibility and speed

- Hardware development
-- Bitter-like high-field electromagnets
--- UHV compatible
--- Novel design using laser-cut copper, PEEK/Mica insulation, interleaved windings
--- Welded connectors (spot welders *can* weld Copper)
--- Designed for keyhole assembly through minimal aperture.
--- Suitable for RF operation at 13.56 MHz or long-pulse high-field operation.

-- Sub-nanosecond optical synchronization system
--- GPS-Disciplined Rubidium master 
--- MOSFET gate-drivers and fast LEDs for trigger generation
--- Trigger distributed over cheap plastic optical fiber
--- Optical gating of microcontroller output using HEMTs, MOSFETs.

-- 3D-printed structuring of (Rogowski-, field-)coils, inductors.
--- 3D-printed wireguides, coilforms allowed high-than-usual precision inductors, high-speed Rogoswki coils
--- 3D-printed coilforms allowed construction of low-capacitance air coils for HV isolation.

-- Inexpensive Solutions to complex problems
--- Party balloon helium leak detector
--- Foil baking-tray Faraday Shield
--- Air-core isolation transformer based on Christmas Wreath from Michaels
--- 3D printed optimal-constraint flexure fixture for lathe levelling
--- Vacuum feedthroughs using spark plugs
--- Sand-filled laser-cut box for fragmentation protection from turbopump
--- Straylight suppression using aligned CNT coatings
--- Etching piezo electrodes using laser printer toner transfer
--- High power resistors from PVC pipe, salt water.
--- Constrained-layer damping for silencing pumps

-- Thomson-scattering Spectrometer employing Spatial Heterodyne method, 200 Watt CW laser.
--- Compact lighpath, online power monitoring via beam splitter.
--- Half-wave plate and optical stage for rotation of polarization
--- Spherical mirror for signal optimisation
--- Readout via fast photodiode, spectrometer
--- Coated laser cut panels for scattered light suppression
--- Script provides automated per-shot baseline.
--- Single shot density measurement at 10 microsecond exposure.

-- Sub-nanosecond 5 kV, kA MOSFET switches
--- Design in SPICE, KiCAD
--- SMT layout in KiCAD, optimised for controlled gate impedance
--- Integrated voltage, current monitors in last generation
--- Fully isolated trigger, supply, readout
--- Optically triggered

-- 10kA, 3kV SCR high-side switch
--- Rectified-flyback trigger and RC filter for isolated triggering, driven by AWG
--- Input impedance matched to 50 ohm.

-- Custom UHV feedthroughs
--- Hand-machined compression fittings, Buna O-rings, good to 10^-8 Torr.
--- Unit cost ~$10

-- High CMR, 100MHz Instrumentation amplifiers
--- Response DC-100MHz, 1kV Common-mode voltage, 50-Ohm output
--- Design based on chopper-stabilised OP-amps

-- 100A, kV electron guns
--- In-house CNC-machined electrode structure
--- In-house etched ferroelectric cathodes
--- Custom-built matching transfomer, pulse generator trigger
--- Custom-built faraday cups, Rogowski coils, GMR sensors, CTs, for current measurement

-- kW RF matching Hardware
--- Surplus vacuum capacitors, hand-built bias tee 
--- First-stage matching by off-the-shelf HAM-radio antenna tuner
--- Tuning using VNA

-- Pulse generators (Blumlein, Flyback, Marx)
--- Parallel DIN + RG58 assemblies for high voltage tranmission at low impedance
--- Avalanche transistor low-side switch; differential mode choke for current-sharing.
--- Power-MOSFET-switched inductive flyback generator.
--- Avalanche-diode marx generator with avalanche-transistor trigger

-- Antenna design for microwave interferometry
--- Helical log-spiral antenna for ultra-wide bandwidth, high directivity
--- Design in mathematica, Autodesk Inventor, KiCAD.
--- Fabricated as PCB with surface mount SMA connector.

-- Xray spectrometry
--- Homebuilt collimators, mounting, trigger
--- Homebuilt water-cooling system for shot noise reduction

- Infrastructure
-- Built up facility from warehouse to laboratory
--- Assembled structures and furniture
--- Rewired USMC EMC shelter; modernised lighting and panel
--- Wired a second shipping container for 3-phase power
--- Installed security systems
--- Ran data and optical cabling and built up computer systems
--- Set up a surface-mount assembly facility
--- Microcontroller supervision of facility power using PLC

-- Container-based RF-shielded lab spaces using optical networking
--- Large EMI filters, UPS isolation of internal equipment prevents interference with outside world
-- Model-predictive HVAC control 
--- Held container to +/- 0.1C over widely varying loads using off-the-shelf minisplit AC
--- IR emitter spoofing remote control
-- Secure multi-site VPN using vxlan over wireguard
--- DDNS establishes name for central server
--- Mobile nodes establish wireguard link, setup vxlan
--- Allows use of lan-local protocols over WAN for mobile laptops
--- Translation performed by travel routers to allow for untrusted endpoints

-- Data-Diode-isolated airgapped secure networks
--- Media translators with one fiber disconected make excellent cheap data diodes
--- Custom software uses FEC to transmit reliably across the gap
--- Enforced-low-bandwidth reverse signalling using relay, optocoupler.

-- InfluxDB, Grafana for visibility

Postdoctoral Research Associate 2016 — 2018
University of Sydney Sydney, Australia
- Design, Construction, Analysis, and Integration of:
-- Magnetically shielded IEC device
--- Coil shells made from plumbing supplies (pipe elbows)
--- Hand-wound coils held in place with cyanoacrylate, then epoxied.
--- Insulation between coils and shell good to 14kV.

-- 40MW pulsed coil power supply
--- One 19" rack full of electrolytic capacitors
--- Heavy copper busbar
--- LED indication of charge state 
--- SCR triggering

-- 50 kV, 6A, stacked-MOSFET HV switch
--- Common-primary, multiple secondary magnetic trigger

-- Sequencer
--- 16 channel PMOS switch, driven by arduino
--- Tk GUI allows upload of timing waveform, compiled on device to unconditional code
--- Interrupt-driven trigger; software abort.

-- Swept, articulated 5kV Langmuir probe
--- Articulation using stepper motor, bellows stage, Arduino-driven H-bridge
--- HV generation using resonant operation of a Bosch car ignition coil. 
--- Current monitoring using fiber-optocoupler.

-- 1 kV microwave source
--- Custom controller for magnetron

-- H𝛼 Spectrometer
--- Initially, modular spectrometer plus filter
--- Ultimately, monochromator plus intensified CCD
--- USB-triggered DSLR camera for image capture.

-- Thermal and Fast neutron detectors
--- Stilbene-crystal scintilator and photomultiplier tube
--- CsI detector
--- He3 ionisation detectors
--- Initially, Multichannel analyser for readout
--- Ultimately, oscilloscope raw capture and matched timedomain filter.

-- Distributed real-time control system
--- Experiment console accepts python-like commands
--- Embedded computers run FORTH

- Theory:
-- Scaling of desktop fusion systems
-- PIC Vlasov-Poissonl Simulation

Honorary Associate 2014 — 2016
University of Sydney Sydney, Australia
- Sotware development
-- Relativistic N-body Maxwell-Particle code (MaxRel)
--- Based on observation that regular kinetic models are invalid for IEC devices
--- Brute-force calculation, but including screening from v/c terms.

-- US/Japan conference presentation on Shielded Grid IEC
--- Presented a paper talking about the expected consequences of trying to model IEC plasmas using MHD
-- Published paper on shielded-grid IEC concept
--- Derived a Hull-esque cutoff for grid current for a shielded grid.

Site Reliability Engineer Dec 2010 — 2014
Google Sydney / New York
- Blobstore
-- Responsible for engineering and disaster recovery for a planet-scale multi-PB deduplicating datastore
-- Spearheaded focus on tail latency and availability
- Kansas
-- Also worked on Kansas (high availability key-value) and Drive teams.
-- Automated Capacity planning tools
-- Spearheaded focus on latency and availability
- Google Drive
-- Load management automation for Google Drive
--- The approach was to migrate lightly-used documents away from heavily-loaded servers
--- The previous approach had moved the most-heavily-used documents, which was pessimal
- Modified
-- Client and server logic to improve performance and reliability
-- Internal libraries and languages to provide richer, simpler monitoring
- Built
-- Process control systems and Instrumentation
-- Better visualisations
-- Generated some wireless application patents

Founder 2009 — 2010
Trooli Perth, Australia
- Wrote software to use Bayesian networks to estimate reliability of information
- Developed distributed prototype in Erlang
- Multi-user beta-test
- Acquired patent protection in EU, USA, Australia

Senior Scientist Feb 2008 — Nov 2009
Senior Scientist Perth, Australia
- Worked with Petroleum and Potash divisions to go from survey data to consistent 3D models of resources
- Built 3D graphical simulation software for CSEM surveys
- Extended the state of the art in nonlinear inversion for seismic and EM data
-- Reversible-jump MCMC software and the Aikake Information Criterion to avoid overfitting.
- Set up a distributed computing environment using XGrid
- Published paper in J. Geophysics in collaboration with the Commonwealth Scientific and Industrial Research Organisation.

Skills
- General: Doing things, safely, with 0.1% of the usual budget.
- Domains: Systems Engineering, SRE, Physics, Electronics, Embedded Systems
- Programming Languages: JavaScript, Python, C/C++, Julia, HTML/CSS, Bash, R, Smalltalk, Verilog
- Technologies: SPICE, Git, UNIX, KiCAD, Docker, NGINX, UDP, TCP. Mathematica