Glossary

TCT

Transient Current Technique. Measures the transient current induced by laser-generated charge.

DUT

Device Under Test. The sensor being measured.

Depletion region

The region free of mobile carriers where the electric field is present. Charge created here contributes to the signal.

Full depletion voltage (\(V_\text{fd}\))

The voltage at which the whole sensor thickness is depleted.

Weighting field

The field obtained with the electrode of interest at 1 V and all others at 0 V. Used to compute induced currents with the Shockley–Ramo theorem.

CCE

Charge Collection Efficiency.

LGAD

Low Gain Avalanche Detector. A silicon sensor with an internal gain layer providing gains of about 10 to a few tens.

PIN diode

A basic diode sensor without a gain layer. Used as the reference for LGAD gain measurements.

MIP

Minimum Ionizing Particle.

Fluence

Number of particles per unit area. Often expressed as 1 MeV neutron equivalent (n_eq/cm²).

Trapping

Capture of carriers by defect levels created by radiation damage.

Edge-TCT

TCT in which the laser enters through the side face of the sensor and is scanned in depth.

TPA-TCT

Two-Photon Absorption TCT. Uses two-photon absorption to obtain 3D resolution.

CFD

Constant Fraction Discrimination. Determines the time at a fixed fraction of the amplitude.

Bias tee

A component that separates or combines DC bias and RF signals.

Terms specific to the Hiroshima setup and GUI

AC-LGAD

AC-coupled LGAD. A structure with a continuous n+ resistive layer and AC-coupled electrodes on top of the LGAD gain layer. The signal spreads through the resistive layer and is shared among several electrodes, giving a position resolution finer than the electrode pitch.

ePIC / bTOF

The ePIC experiment at the EIC (Electron-Ion Collider) and its barrel time-of-flight detector. It uses AC-LGAD strips.

laser_gui

The control GUI of the Hiroshima TCT setup (AC-LGAD Laser Scan Control GUI). Operates the scope, stage, laser and camera from a single window.

TUNE

The PiLAS laser setting [%] that sets the pulse intensity. 0 % is strongest, 100 % weakest. The optimal value changes with the repetition rate.

TRIG OUT

Trigger output of the laser controller. Fed into the external trigger (EXT) of the scope and used as the time reference.

Logical coordinates / logical origin

Sensor-based coordinates [µm] used by the GUI. The origin is X = frame (GND) edge, Y = electrode center of the reference CH, Z = focus.

Machine coordinates / mechanical origin

Coordinates measured from the mechanical origin (H:W) of the stage controller. The GUI tracks them across R:W.

H:W / R:W / M:W / L:W

SHRC-203 commands. H:W is mechanical homing, R:W resets the logical origin (sets the current position to 0), M:W is a relative move, L:W is stop.

M-ORG

Mechanical homing from the joystick JS-301. It breaks the GUI's machine coordinate tracking, so use H:W from the GUI instead.

Origin finding

Procedure that uses the laser signal as a ruler to find the focus, electrode center and frame edge automatically and set the logical origin.

Full calibration

Origin finding plus measurement of the sensor tilt coefficients dY/dX, dZ/dX and dZ/dY.

Sequence mode / segment

Scope mode that acquires many waveforms, one per trigger (segments), in one batch. 2000 segments per point is standard.

PAVA / PKPK

LeCroy waveform parameters. The GUI uses them to read amplitudes (PKPK is peak-to-peak).

TRIGTIME

The trigger time of each segment in a LeCroy sequence waveform. Used as the origin of arrival times.

VICP

LeCroy's own LAN control protocol (port 1861).

MIP-equivalent

State in which the laser pulse height is matched to the MIP signal measured in a beam test (e.g. 64 mV for the adjacent 2-ch sum at the strip midpoint in the DESY beam test).