Isotope Explorer user's manual

Logical operations

Operations, Logical operations can be used for storing gated spectra, for more complicated coincidence relations and for comparing spectra.

It is important to understand the difference between coincidences and logical operations on spectra: double coincidences always show the correct coincidence relations, while the logical operations compare spectra.This means that if the gating transitions are in coincidence the methods are equivalent, otherwise not (see examples below).

When the Operations, Logical operations is selected, the following panel appears:

The panel contains one field describing the current gate, and four memory locations A-D. The white fields are only labels, and entering text in them does not change their properties. The buttons do the following:

Store

Store current gate and spectrum in a memory location (A-D)

Recall

Recall a gate/spectrum from a memory location (A-D)

And

Perform a logical AND between the current gate and a gate from memory location A-D

Or

Perform a logical OR between the current gate and a gate from memory location A-D

Diff

Perform a logical XOR (exclusive or) between the current gate and a gate from memory location A-D

Exch

Exchange current gate with gate in memory location A-D

Reset

Reset current gate to All

Gate

Set energy gate

Coin

Calculate coincidences with currently marked gamma(s)

Undo

Undo last operation

OK

Close logical operations box

A gate is entered into memory A in the following way:

1. Click on the gating gamma or gammas. The selected gamma(s) will turn purple
2. Click the button
3. Select AND or OR, and click OK. The gating gammas are shown in blue (purple if they are in the gate), and coincident gammas are shown in red
4. Select Operations, Logical operations
5. The top panel will now contain a description of the gating condition
6. Store this gating condition (and the resulting spectrum) by clicking Store, A

The following simple example illustrates the use of logical operations. The decay scheme is as in the figure.

	Singles	Coin.		Double Coin.		Logical operations
E(gamma)		347	826	AND	OR	AND	OR	DIFF
347	1	0	1	0	1	0	1	1
826	1	1	0	0	1	0	1	1
1173	1	0	0	0	0	0	0	0
1333	1	1	1	1	1	1	1	0
2159	1	1	0	0	1	0	1	1
2505	1	0	0	0	0	0	0	0

The first table shows the results of gating on the 347 and 826 keV transitions. It can be seen that since the two transitions are in coincidence, the result of double coincidences (both AND and OR) is identical to the result of logical operations on the gated spectra.

	Singles	Coin.		Double Coin.		Logical operations
E(gamma)		347	1173	AND	OR	AND	OR	DIFF
347	1	0	0	0	0	0	0	0
826	1	1	0	0	1	0	1	1
1173	1	0	0	0	0	0	0	0
1333	1	1	1	0	1	1	1	0
2159	1	1	0	0	1	0	1	1
2505	1	0	0	0	0	0	0	0

The second table shows the results of gating on the 347 and 1173 keV transitions. It can be seen that since the two transitions are not in coincidence, the result of the double AND coincidence is different from the result of the logical AND operation on the gated spectra.

Comments to: F Chu (program), P Ekström (manual)

All contents copyright © 1996, Isotopes Project, Berkeley Lab. All rights reserved.
Revised: