Measure the flux at the sample plane and the sample temperature at the same moment, then repeat the run in the dark with the reactor held at that measured temperature. Without the matched dark control, a photothermal enhancement cannot be separated from ordinary thermal catalysis, and the synergy number will not survive review.
The thermocouple that closes the control loop is measuring the reactor wall, and the wall is not where the light lands. In a photothermal experiment the sample is heated from two directions at once — by the beam and by the block — and the two are coupled through the gas, the window and the bed.
The offset between setpoint and sample therefore grows with flux, with pressure, and with the distance between the window and the bed. It is not a constant that can be calibrated once and reused, which is why a reactor that holds ±1 °C at its control point can still run the sample well away from the intended condition.
Each quantity in a photothermal experiment has to be measured where it acts, and one sensor cannot serve two of them.
Log all three faster than the effect you are chasing. The PLR MSCRD-I records at 1 min⁻¹, which resolves a flux step and still keeps a long run readable.
The window sets the spectrum you can deliver, so the reactor constrains the source more than the source constrains the reactor. Sapphire transmits broadly and tolerates high temperature; a coated window can absorb a noticeable share of the beam and warm up while doing it.
| Reactor | Temperature range | Pressure | Window | What it means for measurement |
|---|---|---|---|---|
| PLR MSCRD-I | RT–100 °C, ±1 °C | 0–0.5 MPa | Cell of 50×50 mm or 100×100 mm | Light, heat, electric and magnetic fields in one cell; logging at 1 min⁻¹ suits step experiments |
| PLR-HTSR 2.0 | RT–500 °C, ±1 °C | 0–1.0 MPa | Sapphire Φ30 mm, transmission >90 % | Window stays clear at temperature and passes most of the beam across the full range |
| PLR-GPTR50 / 50T | 300 °C / 400 °C | Gas charge 50 mL | Transmission >97 % | Ten-segment ramp at ±0.5 °C makes the dark control reproducible |
| PLR-PTSR II | 550 °C | Control 0.3–1.6 MPa; measurement 0–1.6 MPa at ±0.25 % FS | 0.19–5 μm, Φ35 mm | Broad window passes both the excitation band and the infrared used for heating |
Read the table as a sensor-placement aid, not a ranking. A reactor with a small gas charge and a slow programmed ramp makes a matched dark run easy to hold; a cell that accepts external fields needs the thermocouple routed so its reading is not disturbed by the field, and the offset re-checked with the field on.
The only valid baseline is a dark run at the temperature the sample actually reached under illumination, not at the setpoint you typed in. Set the block so the sample thermocouple reads that value, wait for the drift to settle, and confirm with the same sensor in the same position.
Then report three numbers rather than one: the light-only rate at controlled temperature, the dark rate at the matched temperature, and the combined rate. The enhancement is the combined rate minus the matched dark rate. Subtracting the light-only rate instead measures the photothermal effect plus the thermal effect and overstates the synergy.
Watch for the case where the dark run cannot reach the sample temperature without the beam. If the block cannot supply it, the experiment has no valid baseline, and the honest response is to report the illuminated rate with its measured temperature and stop there.
A source for photothermal work has to deliver measurable flux and switchable output; everything else is secondary. Xenon delivers visible and infrared together, which is what the experiment wants and what makes attribution hard, so use a UV-cut or water filter when the claim is thermal-only.
The PLS-SXE300E provides 300 W of lamp power with 50 W of total optical power and 150–300 W adjustment, so flux can be stepped without changing the geometry. The PLS-SME400E H1 offers 100 W of total optical power, of which 55 W is visible and 6 W ultraviolet, which suits a cell where a larger window has to be filled.
An LED head is the cleaner choice when heating must come from the visible band alone. The PCX-50C runs nine 10 W channels with a water-cooled circuit from −10 to 80 °C, so the array can be held at a fixed temperature while the sample is heated only by the beam.
Yes, if the sample thermocouple — not the control sensor — reaches the same value as in the illuminated run. A block heater produces a different gradient from beam heating, so match the measured sample temperature and state in the method that this is what you matched.
Step the flux and watch the response. A sensor in the bed responds within seconds and settles; a sensor on the wall responds slowly and overshoots. Comparing two positions during a step is the fastest check, and it also quantifies the offset you have to report.
It depends on the claim. If the mechanism is heating in the visible, a UV-cut filter removes a variable you cannot otherwise control. If the source is meant to represent sunlight, keep the full spectrum and report it with the flux.
