Detector Characteristics
Detector Quantum Efficiency
| Blue Channel Detectors | ||||||
|---|---|---|---|---|---|---|
| Chip | 350 nm | 400 nm | 500 nm | 650 nm | 900 nm | 1000 nm |
| 1 | 53.8 | 81.3 | 85.4 | 78.8 | 28.3 | – |
| 2 | 56.1 | 83.7 | 88.2 | 80.1 | 27.3 | – |
| 3 | 53.8 | 81.1 | 83.8 | 76.8 | 27.4 | – |
| 4 | 56.3 | 77.7 | 80.5 | 75 | 28.3 | – |
| Red Channel Detectors | ||||||
|---|---|---|---|---|---|---|
| Chip | 350 nm | 400 nm | 500 nm | 650 nm | 900 nm | 1000 nm |
| 1 | – | – | 95.1 | 96.7 | 57.0 | 13.2 |
| 2 | – | – | 82.8 | 90.2 | 53.2 | 11.8 |
| 3 | – | – | 84.3 | 90.6 | 51.5 | 11.2 |
| 4 | – | – | 87.4 | 95.7 | 54.4 | 11.2 |
Gain and Readout Noise
The gain, readout noise and approximate bias level for each of the science detectors are listed in the tables below. The bias levels are not stable throughout the night, in particular the bias level decreases after the camera is turned on and only reaches a stable value after 20-25 biases. See the discussion in “Looking at your data” for more details about the overscan regions. The dark current is negligible, 0.01 ADU/s.
We remeasure the gain and readnoise whenever a controller is swapped and will plan to repeat these measurements in September 2023.
| Blue Channel | |||
|---|---|---|---|
| Chip | Gain1 (e-/ADU) | Readout Noise2 (ADU) | Bias level2 (ADU) |
| 1 | 1.96 | 4.9 | 310 +/-8 |
| 2 | 2.09 | 5.9 | 353 +/-8 |
| 3 | 2.06 | 5.1 | 320 +/-9 |
| 4 | 1.98 | 5.5 | 315 +/-11 |
| Tech 13 | 5.5 | ||
| Tech 23 | 5.2 | ||
| Red Channel | |||
|---|---|---|---|
| Chip | Gain1 (e-/ADU) | Readout Noise2 (ADU) | Bias level2 (ADU) |
| 1 | 2.08 | 6.0 | 243 +/- 10 |
| 2 | 2.14 | 7.4 | 167 +/- 20 4 |
| 3 | 2.13 | 5.7 | 245 +/- 8 |
| 4 | 2.09 | 5.5 | 231 +/- 7 |
| Tech 13 | 6.0 | ||
| Tech 23 | 8.0 | ||
- Gains were remeasured in 2017 with controller 6 (Blue) and controller 1 (Red) and the values: LBCB 1.5, 1.8, 1.7, 1.8 and LBCR 1.8, 2, 2, 2 for chips 1, 2, 3 and 4; are consistent with the those provided in the commissioning reports.
- For the science chips, the readout noise and bias values are from Sep 05-28 2022. The error represents the standard deviation in the average bias level over time. The readnoise is the standard deviation of each bias (averaged for all of the biases from Sep 2022).
- Tech chip readnoise from lab measurements (?)
- The bias level on LBCR chip 2 is lower and more variable than on other chips; this has been noticed since early 2022 and with two different controllers.
Linearity
During instrument commissioning, the linearities of the LBCB and LBCR science detectors were measured. Deviations from linearity were ~1% at saturation, 65535 ADU.
