The nscan() plan – scan multiple axes together

In this example, we demonstrate the apstools.plans.nscan() plan. The nscan() plan is used to scan two or more axes together, each in equally spaced steps, such as a \(\theta\) - \(2\theta\) powder diffractometer scan.

Here, we scan two motors together, each in equally spaced steps. We use an swait record (part of the userCalc support from synApps) as a detector. We configure the swait record with a calculation (from setup_random_number_swait() in apstools.synApps) that computes a noisy (random number) signal.

Setup

For this demo, we do not need the databroker since we do not plan to review any of this data after collection. We’ll display the data during the scan using the LiveTable() code.

from apstools.synApps import UserCalcN, setup_random_number_swait
from apstools.plans import nscan
from bluesky import RunEngine
from bluesky.callbacks import LiveTable
from ophyd import EpicsMotor

RE = RunEngine({})

Set the prefix for the EPICS IOC that provides the PVs we’ll use here.

IOC = "gp:"

Connect to our motors and create the noisy detector.

m1 = EpicsMotor(f"{IOC}m1", name="m1")
m2 = EpicsMotor(f"{IOC}m2", name="m2")
noisy = UserCalcN(f"{IOC}userCalc1", name="noisy")

m1.wait_for_connection()
m2.wait_for_connection()
noisy.wait_for_connection()

# configure the *detector* as a random number generator using a calculation.
setup_random_number_swait(noisy)

Scan

Measure the noisy detector while step scanning both the m1 & m2 motors together. We’ll move m2 twice as far as m1, like a \(\theta\)-\(2\theta\) scan on a diffractometer.

RE(
    nscan([noisy, ], m1, 2, 0, m2, 4, 0, num=6),
    LiveTable(["m1", "m2", "noisy_val"])
    )

+-----------+------------+------------+------------+
|   seq_num |       time |         m1 |         m2 |
+-----------+------------+------------+------------+
|         1 | 00:22:27.5 |    2.00000 |    4.00000 |
|         2 | 00:22:28.6 |    1.60000 |    3.20000 |
|         3 | 00:22:29.7 |    1.20000 |    2.40000 |
|         4 | 00:22:30.8 |    0.80000 |    1.60000 |
|         5 | 00:22:31.9 |    0.40000 |    0.80000 |
|         6 | 00:22:33.0 |    0.00000 |    0.00000 |
+-----------+------------+------------+------------+
generator nscan ['fcb9a1ad'] (scan num: 1)

('fcb9a1ad-1901-4955-96df-f2079f4edd1c',)