ALOHA · A LINEAR OPEN-HARDWARE ACCELERATOR
ALOHA, A Linear Open-Hardware Accelerator, is built in stages, ordered by risk and by who will use them; the numbers follow the order they were proposed. We aim to design, simulate, build and document each one in the open before the next.
ALOHA-1, the line. Schematic, not to scale.
STAGE 0 · DEMONSTRATOR
A glow-discharge demonstrator that makes the path of a beam visible. It brought Edwards Vacuum on board as our first sponsor.
| QUANTITY | VALUE | STATUS |
|---|---|---|
| Pressure, operating | 1.7 Torr | MEASURED · PIRANI GAUGE · 7 JULY 2026 |
| Supply, isolated | 10 kV | BUILT |
STAGE 1 · THE ELECTRON SOURCE
The electron source: a thermionic telefocus triode. A tungsten hairpin cathode and a Wehnelt cylinder at −20 kV face a grounded anode, and the Wehnelt shapes the emission so the beam focuses far beyond the anode. The 20 keV beam ends on a graphite collector inside a closed chamber, which stops it and measures its current. We build it once, to the beam requirements of ALOHA-2.
| QUANTITY | VALUE | STATUS |
|---|---|---|
| Beam energy | 20 keV | DESIGN |
| Beam current | <1 mA | DESIGN |
| Extraction voltage, as simulated | 30 kV | SIMULATED · COMSOL |
| Beam current, as simulated | 1.5 mA | SIMULATED · COMSOL |
| Beam spot, as simulated | <1 mm | SIMULATED · COMSOL |
| Cathode | W hairpin, thermionic | DESIGN |
| Beam stop | Graphite collector | DESIGN |
| Experiment | Smith-Purcell sub-THz | PROPOSED |
STAGE 2 · THE INSTRUMENT
ALOHA-0 plus a target that turns its beam into X-rays, a window that lets only the X-rays out towards a painting, an energy-dispersive detector, shielding and a scanning stage. At 20 keV it reads the core of a restorer’s palette without taking a sample; the 20 keV ceiling protects the paintings.
| QUANTITY | VALUE | STATUS |
|---|---|---|
| Beam energy | 20 keV | DESIGN TARGET |
| Technique | X-ray fluorescence | PROPOSED |
| Elements read | Ca, Fe, Cu, As, Hg, Pb | DESIGN TARGET |
| Use | X-ray spectroscopy of pigments | AIM |
STAGE 3 · ACCELERATION · CONDITIONAL
Adds pre-acceleration, a buncher and an accelerating structure at 2.998 GHz, fed by a second ALOHA-0, up to 1 MeV, with an experiment at the end of the line. It is conditional: we build it once a research group commits to using it. Until then it advances without beam, in the design and cold tests of its cavities.
| QUANTITY | VALUE | STATUS |
|---|---|---|
| Beam energy | 1 MeV | DESIGN TARGET |
| RF frequency, S-band | 2.998 GHz | DESIGN |
| Buncher | 4 cavities | DESIGN |
| Accelerating structure | 4 cavities | DESIGN |
2026-27
The least we aim for: the vacuum system, pumped down and measured, with its control electronics tested.
VACUUM SYSTEMSEMESTER 1 · BUILD
VACUUM CONTROLSEMESTER 1 · BUILD
CATHODE SUPPLYAFTER THE VACUUM · DEPENDS ON FUNDING
OPEN DOCUMENTATIONTARGET · BEFORE JANUARY 2027
ALOHA-2 REQUIREMENTS MEETING2026-27
ALOHA-1 CAVITY DESIGNDESIGN · THROUGH THE SEASON
OPEN
The hardware licence: strongly reciprocal, so whatever is built from our designs stays open too.
The public record of the design process: reports, inputs and the reasoning behind every number.
COMING · THE DOCS REPOSITORY
How the team works, as a public online book.
EDITION 2026-27