Lawrence Berkeley National Laboratory 88-Inch Cyclotron

The 88-Inch Cyclotron hosts the Berkeley Accelerator Space Effects facility, one of the off-site heavy ion beams JPL’s radiation effects group sends parts to [3]. What distinguishes it is the cocktail: a set of ions of nearly identical charge-to-mass ratio accelerated together, from which the operator selects a species by retuning the cyclotron frequency alone. Because the machine resolves mass to one part in 3000, a species change takes about two minutes [1]. A full cross section against linear energy transfer curve can therefore be measured in one shift, which is the opposite of the position at the NSCL facility, where a species change costs a day.

The cost of that is energy. The cocktails top out at 30 MeV per nucleon, giving ion ranges in silicon of 40 to 1400 micrometers, so most parts must be depackaged and many flip-chip parts thinned before they can be tested here [1][2].

JPL was a founding user of the facility and has run tests there continuously since, holding it adequate for practically all single event effect testing called for under JESD57 and ASTM-1192 [3]. JPL’s own account groups it with two other off-site heavy ion beams it routinely uses, Brookhaven’s Tandem Van de Graaff and the RADEF facility in Finland, and separately notes proton testing experience at LBNL outside the heavy ion cocktails described here [3]. That fast species change is what earns the low-energy label: a 1999 handbook for Space Shuttle Orbiter avionics groups the 88-Inch Cyclotron with the Brookhaven Tandem Van de Graaff and the Texas A&M K-500 as facilities for low-energy heavy ion testing, set against the Indiana University Cyclotron Facility for high-energy protons and the higher-energy Michigan State cyclotron for testing that avoids de-lidding [9]. A 2021 NASA hardness assurance guideline updates that comparison: Texas A&M’s K-500 reaches heavier ions at higher energy, gold at 15 MeV per nucleon against LBNL’s bismuth at 30 MeV per nucleon, and can run in air, while LBNL changes species faster and runs in vacuum; both facilities were planning upgrades as of that writing, and the Brookhaven NASA Space Radiation Laboratory sits above both at up to 400 MeV per nucleon, penetrating centimeters of silicon without de-lidding at all, extracting its beam in 0.3 to 0.4 second spills separated by about 3.6 seconds of beam-off time, a duty cycle the 88-Inch Cyclotron’s continuous cocktail beam does not share [10]. The same 1999 handbook notes that facilities reaching roughly 80 MeV per nucleon in heavy ions can penetrate devices without de-lidding them at all, unlike the 88-Inch Cyclotron’s 30 MeV per nucleon ceiling, which is why system-level testing on assembled boards tends to move to those higher-energy machines instead [9]. A wider industry-wide comparison, spanning a dozen proton and heavy ion beams and using energy as the common axis for protons and LET for heavy ions, places the 88-Inch Cyclotron among the facilities whose package modification requirements are the most severe for flip-chip parts [2]. That table is meant to help a test planner pick a facility before writing the test plan rather than after, matching device package against the four columns of required modification it lists [2]. The facility did not always sit at this point in the landscape. A 1984 JPL guideline for heavy ion single event upset testing, written before cocktail beams existed, lists the same UC Berkeley cyclotron as one of three candidate US machines, at ion intensities of 1e3 to 1e5 ions per square centimeter per second, two to four orders of magnitude below the present flux [8]. That guideline’s baseline requirements for any candidate facility, a beam of adequate and uniform intensity, steering on two orthogonal axes, and real-time flux measurement, are what the cocktail beam described above satisfies by a wide margin rather than marginally [8].

Laboratory data

Parameter	Value
Operator	Lawrence Berkeley National Laboratory [3]
Location	Berkeley, California, United States [3]
Commissioned	Not published
Type	Cyclotron: heavy ion, light ion and neutron irradiation for single event effects
Floor area	Not published
Capabilities	Heavy ion, Cave 4B, light ion, Cave 4A
Simulant or terrain	Not applicable
Instrumentation	Four-quadrant concentric ion chambers; Gafchromic film; cave phosphor and photomultipliers [1]
Ground truth	Per-ring flux and fluence with programmable fluence stop; uniformity by film [1]
Fidelity limits	Monoenergetic single-species beam; 30 MeV/u ceiling forces depackaging [1][2]
Access	User facility; about 2000 beam hours per year across all programs [1]
Cited by	radiation testing, FPGAs and logic

Capabilities

Heavy ion irradiation facility

Parameter	Value
Working volume	Vacuum chamber in Cave 4B; dimensions not published [1]
Test article limits	Ceramic cover removed; flip-chip thinned, or not tested at the high LET tune [2]
Vacuum	Yes. Heavy ion exposures are run in vacuum [4]
Temperature	Not published
Illumination	Alignment laser; beam spread to 5 cm on a cave phosphor for tuning [1]
Slope	Not applicable
Gravity offload	Not applicable
Instrumentation	Remote horizontal, vertical and rotational positioning on a motion table [1]

Four standard cocktails run at 4.5, 10, 16 and 30 MeV per nucleon, together covering linear energy transfer from 1 to 100 MeV-cm2/mg at ranges in silicon of 40 to 1400 micrometers and flux up to 1e7 ions/cm2/s [1][3]. Read as two working tunes rather than four cocktails, the envelope a test planner sees is 2 to 100 MeV-cm2/mg at 53 to 80 micrometers of range on the high-LET tune, and 1 to 50 MeV-cm2/mg at 150 to 500 micrometers on the high-penetration tune [2]. On the high-LET tune flip-chip parts should not be tested at all; on the high-penetration tune they can be, thinned, with no heat spreader and no heat sink [2].

Beam cutoff is by manual command, run time, fluence or effective fluence, and a collimated milli-beam in the same cave isolates a single event to 10 to 30 micrometers at best, or 100 to 300 micrometers at higher scan rates, using precision slit collimators [1].

The facility description states no uniformity figure over the irradiation area for the heavy ion chamber, no temperature control and no in-situ bias provisions [1]. A campaign needing elevated-temperature latchup screening therefore brings its own thermal arrangement.

Light ion irradiation facility

Parameter	Value
Working volume	Cave 4A, samples in air; 10 cm beam with 2.5, 5, 7.5 or 10 cm collimators [1]
Test article limits	Set by the collimator and the in-air standoff [1]
Vacuum	None. Samples run in air; low energies can be moved to the Cave 4B chamber [1]
Temperature	Not published
Instrumentation	Four-quadrant concentric ion chamber electrodes at 1, 2, 4, 6 and 8 cm [1]

Standard proton energies are 13.5, 20, 30, 40, 50 and 55 MeV at flux up to 1e9 protons/cm2/s, the low end limited by energy loss in the ion chamber and in the air path [1]. Uniformity is verified with Gafchromic film, and the ring electrodes give flux and fluence per ring with a programmable fluence stop. Neutron beams are produced separately by deuteron breakup on a 125 mil beryllium target for high yield or tantalum for low yield, with absolute flux measured by activation foils [1].

What it does not reproduce

The spectrum. A cocktail beam is monoenergetic and single-species; the galactic cosmic ray environment is neither. The general form of that limit, and what can and cannot be argued from a null result at a given species, is on the radiation testing page.

Penetration through a package. At 5 to 50 MeV per nucleon the ion ranges out in the lid, the heat spreader or the substrate before it reaches the sensitive volume, so parts are depackaged and dies thinned [1][2]. A copper heat spreader cuts ion range to 26 percent of the silicon range [2]. Every result taken here is therefore a result on a modified part, and the modification is part of the test record.

A stated capability is not a measured one. The facility description is the operator’s own, with no independent verification and no measurement of delivered dose against a reference [1].

Campaigns run there

Commercial and radiation-hardened FPGA and memory screening, reported 2020. A NASA survey ran a Xilinx XCKU040 Kintex UltraScale, a Microsemi MPF300T PolarFire and several 3D NAND and MRAM parts here [4]. The PolarFire, thinned to 100 to 120 micrometers, gave a configuration memory upset threshold below 1.16 MeV-cm2/mg at about 3e-7 cm2 per design, and a single event functional interrupt at the same threshold, the core current dropping below 100 mA for 1.7 ms and requiring a system reset [4]. The Kintex UltraScale configuration memory upset threshold was below 0.07 MeV-cm2/mg without scrubbing. On the memories, a Micron MT29F1T08 3D NAND showed no latchup to LET 85 at 78 C, a Hynix H25QFT8F4A9R showed a destructive event at 58.8 MeV-cm2/mg at 80 C on two of two parts, and an Avalanche 40 nm MRAM latched between 21.1 and 58.8 MeV-cm2/mg [4]. The PolarFire run was a first look at the device and beam time was cut short by wildfires that year, so only nitrogen, oxygen and neon at 16 MeV per nucleon were available rather than the full cocktail set [4].

Point of load converter single event characterization, reported 2019. The Analog Devices RH3845 step-down controller was exposed to yttrium in vacuum through a 2 mil Kapton degrader and to xenon in air at 45 degrees from a 16 MeV/amu cocktail [5]. The work spanned separate 2018 and 2019 visits on the 10 and 16 MeV per nucleon cocktails, run to a cumulative fluence of 1e7 ions per square centimeter unless a destructive event stopped the run first [5]. Destructive onset averaged 44 V at PVIN over five flight-lot devices at LET 38, with minimal temperature dependence between -5 C and room temperature, which is evidence against a single-event burnout mechanism. A cross-conduction event with an onset LET of 0.1 MeV-cm2/mg was eliminated by raising the in-line gate drive resistance from 2 to 10 ohms, after which two devices took LET 79 to 1e7 ions/cm2 at PVIN up to 100 V with no destructive failure [5]. The functional interrupt mode was removed by holding a pre-load current above 1 mA, verified on five devices at LET 79 with no events [5].

Wide bandgap logic, reported 2019. A NASA GRC 4H-SiC junction FET clock circuit of 175 JFETs showed a single event upset onset between LET 3.5 and 9.7 MeV-cm2/mg, no upsets under neon at 3.5 and upsets under argon at 9.7, with no destructive effect to LET 86 at normal incidence under gold [6]. Isolated D flip-flops showed no upsets, which localizes the sensitivity to the control logic rather than the storage element, in a run that used the 10 MeV per nucleon tune in vacuum with ion flux held below 2e5 per square centimeter per second to keep individual events separable [6].

Comparator transient screening. The Linear Technology RH1011M comparator’s output transients were fully mitigated by appropriate parasitic output capacitance up to LET 114 MeV-cm2/mg at room temperature and at 100 C, the unfiltered transient cross section being about 1.6 percent of total die area and temperature independent [7]. The same compendium traces LBNL heavy ion testing of bipolar op-amps back to 1992 and 1997 lots, evidence the facility carried JPL’s parts program for two decades before that 2012 comparator run [7].

Orion crew vehicle piece-part and system screening. NASA Johnson Space Center’s avionics program tested commercial and non-commercial parts for the International Space Station and the Orion Multi-Purpose Crew Vehicle across four facilities, splitting the work by need: board and system-level commercial parts took high-energy protons at the Indiana University Cyclotron Facility, individual piece parts took heavy ions at Texas A&M and at the 88-Inch Cyclotron, and Orion system-level testing added the variable depth Bragg peak method at the Brookhaven NASA Space Radiation Laboratory [11], which interposes energy degraders ahead of the sensitive volume to move the Bragg peak rather than changing the beam energy itself, and needs sacrificial samples to calibrate that position against the device response [10]. The heavy ion facilities did the component-level screening that the proton beam and the Bragg peak method could not. Traditional heavy ion testing of the kind run at the 88-Inch Cyclotron requires each part de-lidded and considered individually, with a test plan detailed enough to record exact part numbers and lot date codes; the Bragg peak method exists precisely for the epoxy-filled and flip-chip parts that approach cannot reach [11].

Turning a cross-section curve measured here into an on-orbit rate uses tools such as CRÈME96, SPENVIS or OMERE built on the rectangular parallelepiped model, and a confident rate needs LET coverage up to 60 to 75 MeV-cm2/mg; the high-LET tune’s 100 MeV-cm2/mg ceiling covers that range, but the high-penetration tune’s 50 MeV-cm2/mg does not [10].

High-energy proton testing generally does not require de-lidding the part at all, a contrast with every heavy ion tune described above, and beam quality for proton facilities varies further by scattering technique and by whether the beam is continuous or pulsed in time, variables a test plan comparing results across facilities has to track alongside energy [10]. The same 2021 guideline tells its readers to verify current capability directly with each facility rather than trust a published figure, since the Michigan State cyclotron discussed above was itself under upgrade as of that writing, projected to add beam reaching 200 to 300 MeV per nucleon, energies the 88-Inch Cyclotron’s cocktails do not approach [10].

RF component TID and heavy ion screening for a Europa Clipper-era lot. The Johns Hopkins University Applied Physics Laboratory ran its heavy ion single event effect program primarily at Texas A&M’s K-500, with the 88-Inch Cyclotron’s BASE facility used for additional testing on the same device lot, alongside separate total ionizing dose exposures that found the Analog Devices AD607 IF subsystem’s dynamic range degrading in unbiased parts but not in biased ones over 100 krad [12]. The same program ran its neutron displacement-damage testing at a reactor in Massachusetts rather than at LBNL, keeping the 88-Inch Cyclotron’s role in that campaign to heavy ion single event effects alone [12].

What is not established

The facility’s own description carries the ceiling, the LET envelope and the beam diagnostics, but no held source measures delivered dose against an independent reference, and none gives a fee schedule, a lead time or a queue length beyond the aggregate 2000 annual beam hours shared across all programs at the cyclotron [1]. Nor does any held source resolve which fraction of that time space-effects testing actually gets against the facility’s nuclear physics and other users. The comparative record is a step behind the facility’s own upgrade plans: the 2021 guideline notes both LBNL and Texas A&M were planning upgrades without saying to what envelope, and no later source held here confirms whether either upgrade landed [10]. Campaign reports here are single test dates on specific device lots; a threshold in one report is a property of that lot and that beam tune, not a universal rating for the part number, and none of the campaigns held describes calibration cross-checks against a second facility on the same devices, so no independent read on the cocktail’s declared LET calibration exists here.