TEM3: AutoFlashing Tutorial

This tutorial explains how to run FEG AutoFlashing in a safe sequence.

Target flow:

1. SetBeamValve(0)

2. SetFEGEmissionOff()

3. Poll GetEmissionOnStatus() until it returns (0, 0)

4. ExecAutoFlashing(1)

5. Poll GetAutoFlashingStatus() until it returns 0

6. ExecEmissionOn(1)

7. Poll GetEmissionOnStatus() until it returns (0, 1)

Notes:

• This procedure modifies the actual instrument state. Follow your facility’s operating rules before executing.

• Some FEG3 functions are available only on CFEG instruments.

• GetAutoFlashingStatus() may temporarily return 0 immediately after ExecAutoFlashing(1) is called. This tutorial therefore separates the start-confirmation and completion-confirmation steps.

from datetime import datetime, timedelta
import time

from PyJEM import TEM3

feg = TEM3.FEG3()

def poll_until(check_func, expected_value, timeout_seconds=60, interval_seconds=1, label="status"):
    deadline = datetime.now() + timedelta(seconds=timeout_seconds)
    while datetime.now() < deadline:
        value = check_func()
        print(f"{label}: {value}")
        if value == expected_value:
            return value
        time.sleep(interval_seconds)
    raise TimeoutError(f"Timed out waiting for {label} == {expected_value}")

Step 1. Close beam valve

Close the beam valve first to block the beam before changing the emission state.

feg.SetBeamValve(0)
print("Beam valve closed.")

Beam valve closed.

Step 2. Turn emission off

Stop the FEG emission before starting AutoFlashing.

feg.SetFEGEmissionOff(1)
print("FEG emission off command sent.")

FEG emission off command sent.

Step 3. Wait until emission is fully off

GetEmissionOnStatus() returns (phase, status).
Poll until the value is (0, 0) to confirm that the emission-off sequence has completed.

poll_until(
    feg.GetEmissionOnStatus,
    (0, 0),
    timeout_seconds=120,
    interval_seconds=1,
    label="GetEmissionOnStatus"
 )

Step 4. Start auto flashing

Start AutoFlashing.
The return value is checked as an indicator that the command was accepted.

result = feg.ExecAutoFlashing(1)
print("ExecAutoFlashing(1):", result)

Step 5. Wait until auto flashing completes

GetAutoFlashingStatus() may return 0 (Idle) immediately after ExecAutoFlashing(1) because the flashing has not yet started.
This step therefore first waits until 1 (Running) is observed to confirm the start, then waits for the status to return to 0 (Idle) to confirm completion.

startup_deadline = datetime.now() + timedelta(seconds=30)
finish_deadline = datetime.now() + timedelta(minutes=10)
seen_running = False

while datetime.now() < finish_deadline:
    status = feg.GetAutoFlashingStatus()
    print("GetAutoFlashingStatus:", status)

    if status == 1:
        seen_running = True

    if seen_running and status == 0:
        print("AutoFlashing finished.")
        break

    if (not seen_running) and datetime.now() > startup_deadline:
        raise TimeoutError("AutoFlashing did not enter running state within 30 seconds.")

    time.sleep(1)
else:
    raise TimeoutError("AutoFlashing did not finish within 10 minutes.")

Step 6. Turn emission on

Resume FEG emission after AutoFlashing has completed.

result = feg.ExecEmissionOn(1)
print("ExecEmissionOn(1):", result)

Step 7. Wait until emission is fully on

Poll GetEmissionOnStatus() until it returns (0, 1) to confirm that the emission-on sequence has completed.

poll_until(
    feg.GetEmissionOnStatus,
    (0, 1),
    timeout_seconds=180,
    interval_seconds=1,
    label="GetEmissionOnStatus"
 )