Table of Contents

S800 SpecTcl

SpecTcl is the NSCL's event data analysis tool used for online and offline data analysis during experiments involving the S800 spectrograph. The documentation is accessible at:

The SpecTcl Control has been adapted for special functions required for the analysis of S800 data. SpecTcl can be open by from computer u6pc5 by clicking in the icon SpecTcl located in its desktop, or from a Linux terminal by typing ./SpecTcl from directory /user/s800/operations/spectcl/s800v7 .

Spectra definition files can be found in directory /user/s800/operations/spectcl/s800v7/Definitions. Some pre-defined windows with useful spectra can be found in directory /user/s800/operations/spectcl/s800v7/Windows.

The figure below shows the GUI control of the S800 analysis.


The inverse map which enables the trajectory reconstruction of the particles within the spectrograph beam line can be loaded. Snapshots of CRDC and TPPAC events sampled in the pads and strips can be viewed. If this option is “armed”, the sample is read out for the first event that falls into the specified gate. This is a diagnostics tool to analyze the response of the CRDCs and TPPACs.

The TreeParameter class

The TreeParameter class provides a mean to implement parameters in SpecTcl in a tree-like structure and without the need to specify parameter identification numbers. The parameters are referred to by their names only, which at the same time indicate their location in the tree. This reference mechanism is valid for both the coding part of SpecTcl (C++ code) and the interpreter part (Tcl/Tk shell). It eliminates the confusion induced by the use of numerals to refer to the parameters, and allows the user to organize the parameters in a logical fashion.

Frequently used parameters for S800 SpecTcl

Frequently used variables for S800 SpecTcl

(to be set on the “Variables” page of the GUI) for the CRDCs (n=1,2 for crdc1 and crdc2):

Sample spectra

The following figures depict some of the S800 SpecTcl spectra used for the tunning of the S800.

Energy loss in the ion chamber vs. time of flight measured between the object scintillator and the E1 scintillator (trigger) at the end of the focal plane


(In)elastic scattering of the incoming "cocktail beam" on a Au target (spectrograph in focus mode)


Sn-124 primary beam passing a thick Al viewer at the target position (focused optics)


Upper left: Three 124Sn charge states in the CRDC2 x-y spectrum

Upper right: Amplitude of the CRDC2 anode signal vs. drift time (this is a diagnostics spectrum showing that the response of the CRDC is not correlated with the y position).

Lower left: Raw drift time measured in CRDC2

Lower right: Charge distribution induced in the pads by the three 124Sn charge states hitting CRDC2.