qutools quTAU User manual

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quTAU/quPSI Manual V4.0 (April 5, 2016)

CONTENTS
Contents
1 Quickstart Guide 4
1.1 Setting up your system ............................. 4
1.2 Setting up your device ............................. 4
1.3 Writing your own program ........................... 5
2 Technical Information 6
3 Hardware Concept 6
4 General Information 8
4.1 Bin width/Differential Nonlinearity ...................... 8
4.2 Time tags bit width ............................... 8
4.3 Software Packages ................................ 8
4.4 Linux Support .................................. 9
5 Windows Installation 9
6 Firmware Update 9
7 Software 11
7.1 Concept ..................................... 11
7.2 Daisy ....................................... 12
7.3 quTAU GUI ................................... 13
7.4 Command Line Interface ............................ 13
7.5 Using the quTAU with your own software (Library functions) ....... 14
8 Input Parameter Settings 17
8.1 Software Realizations .............................. 18
8.2 DLL Usage ................................... 18
9 (Coincidence) Counting 21
9.1 Integration Time ................................ 21
9.2 Coincidence Time Window ........................... 21
9.3 Realizations ................................... 21
9.4 DLL Usage ................................... 24
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CONTENTS
10 Time Stamping 25
10.1 Writing and loading Time Stamps ....................... 25
10.2 Software Realizations .............................. 26
10.3 DLL Usage ................................... 27
10.4 Retrieving Timestamps as an Array ...................... 28
11 Histograms 30
11.1 Start-Stop Histograms ............................. 30
11.2 Start-Multistop Histograms: Lifetime Measurements ............. 34
11.3 Correlation Measurements: HBT ....................... 38
12 Simulation and Testing: Demo Mode 43
12.1 quTAU GUI Simulation ............................ 43
12.2 DLL Usage ................................... 43
13 Differences using a quPSI 44
13.1 quTAU GUI ................................... 44
13.2 DLL Usage ................................... 44
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1 QUICKSTART GUIDE
1 Quickstart Guide
1.1 Setting up your system
For a quick start, first install the quTAU software with the default options (see Section 5).
The necessary device drivers, different GUIs for the most common tasks, and a user library
– complete with examples – to support user written programs will be installed. The mostly
self-explanatory quTAU GUI is accessible via the Start Menu under quTAU/quTAU GUI.
It can already be tested and explored even without a quTAU device due to the integrated
demo functionality, see also Figure 1.
Figure 1: The quTAU GUI. By using the menu (1), timestamps can be saved to a file, a
settings dialog can be opened and additional information can be displayed. The tabs (2)
allow access to the different features of the device. Please note the status bar (3) at the
bottom, showing additional information and the state of software and device.
1.2 Setting up your device
After connecting the quTAU device over USB2.0, please check your firmware version with
the provided update utility (in the Start Menu under quTAU/Tools/Firmware Update
Utility, see Section 6for details). Please make sure the device will not loose power or is
switched off while flashing the firmware! If everything is in order, you can start using the
GUI to record and analyze data or write your own program using the functions included
in the tdcbase.dll DLL and the LabViewTM VIs.
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1 QUICKSTART GUIDE
1.3 Writing your own program
The device has to be initialized using TDC init and de-initialized with TDC deInit, ev-
erything else depends on the task at hand. A complete list of all functions the DLL
provides and information about how to call these functions is included as doxygen gen-
erated documentation in userlib/doc/index.html. You can also find descriptions and
examples for the most common tasks in this manual. Working LabViewTM Examples (like
the one shown in Figure 2) are included in the userlib/labviewXX/examples folder in
the installation directoy, C examples can be found in the userlib/src Folder.
Figure 2: Block diagram for a program to retrieve and display Single and Coincidence
Rates , see example countrate plot.vi
Please take note of the information about histogram binning and time tagging in Section 4.
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3 HARDWARE CONCEPT
2 Technical Information
The quTAU is an 8-channel time-to-digital converter with a time bin of 81 ps. The ar-
rival time of incoming signals is recorded, pre-processed (count rates are computed) and
transferred to a PC via USB2.0 for further analysis. The user can read out raw time tags
as well as calculated start-stop histograms.
The basic quTAU model can optionally be upgraded with 3 distinct extensions: The input
hardware extension, enabling to specify input parameters for each channel individually,
and two software extensions for a straightforward analysis of Lifetime and Hanbury-
Brown and Twiss measurements, respectively. Please note that all three upgrades are
already integrated in the quTAU (H+) model.
The key features of the quTAU device are:
•8 channels
•High timing resolution (bin size 81 ps)
•High event rates
•Coincidence counting integrated
•USB2.0 interface
•Easy-to-use
The device can be used for a variety of Applications:
•Time correlated single photon counting (TCSPC)
•Fluorescence lifetime imaging
•Quantum information experiments
•LIDAR
•High energy/accelerator physics
•High precision time measurements
3 Hardware Concept
The hardware of the quTAU mainly consists of an ASIC (converting the incoming signals
in all 8 channels into time tags) and an FPGA (sorting the time tags, detecting coinci-
dences in the first 4 channels and compressing the data for transfer via USB2.0). The
output is limited only by the speed of the USB2.0 connection: Up to 5 million events per
seconds can be transferred.
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3 HARDWARE CONCEPT
Table 1: Input Specifications.
Channels 8
Bin width (ps) 81
Input pulse high level (V) Min 2.4
Max 5
Input pulse width (ns) Min 4
Input pulse separation (ns) Min 5.5
Input Impedance (Ω) (LV)TTL 50/5000
Max event rates (Mevents/s) 1ch counting 10
8ch counting 25
8ch time tags 3
Software Delay (ns) Min -50
Max 50
Figure 3: Hardware concept of the quTAU. An ASIC converts the incoming signals into
time tags, which are then analyzed by an FPGA and transferred to a PC via USB2.0.
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4 GENERAL INFORMATION
4 General Information
4.1 Bin width/Differential Nonlinearity
The width of adjacent inherent time bins (of 81 ps) is not constant, but rather alternating.
After each narrower one, there follows a wider one. This is a characteristic feauture of the
TDC chip in the device and can lead to effects like the time difference histogram shown
in Figure 4.
Figure 4: Result of alternating width of time bins in a time difference histogram
when using an odd number of bins for histogram binning. Instead of a gaussian distribution,
the histogramm shows a comb structure due to the differently wide time bins. This effect
vanishes for even numbers of summed bins.
4.2 Time tags bit width
The internal size of time tags is 56 bit. Therefore, they will overflow after (256 −1)·81 ps =
5836665.12 s = 67.55 d.
4.3 Software Packages
The latest drivers, firmware and software can always be downloaded from our website:
www.qutools.com/download/list.php
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6 FIRMWARE UPDATE
4.4 Linux Support
The quTAU offers Linux support for current major distributions. Although this manual
focuses on Windows users and the quTAU GUI was designed for Windows, most of the
concepts are identical or very similar. If you have specific questions or problems using
the quTAU with Linux, please contact us directly.
5 Windows Installation
•Supply power to the quTAU device via a cattle plug, connect it to a PC using a
USB2.0 cable and switch it on.
•Use the provided installer and follow the instructions to install all necessary com-
ponents.
6 Firmware Update
Attention: Naturally, firmware updates are a delicate process and can poten-
tially harm the device if done incorrectly. Do so only when it’s advised by the
manufacturer. In that case, please read and follow these instructions carefully.
Figure 5: The Firmware Update Utility NHFlash is ready to start the update.
When a firmware update is required, please use the program daisy/nhflash.exe (Firmware
Update Utility in the Start Menu) to do so. The current firmware is located in the
daisy/firmware directory and consists of three files qutau core.bit,qutau appl.bit
and qutau dsp.bit. They contain firmware for the core FPGA (infrastructure), the ap-
plication FPGA (handling the TDC chip) and the DSP of the quTAU device, respectively.
On startup, the update utility checks whether all three files are in place and will tell you
if not. Please stick closely to the following steps:
1. If the device is running, please switch it off.
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6 FIRMWARE UPDATE
2. If any quTAU software is still running, please close it.
3. Turn on the device.
4. Start nhflash.exe from the start menu or the daisy directory. After some time,
the LED should become green and the text ”Hardware ID: 0” (or similar) should
be displayed (see Figure 5).
5. If all of this is satisfactory, please press ”Flash”. The green LED should start
flashing until it is finished. At the end of the process, the LED should be green
again and the text close to it should read ”Update complete”. Make absolutely sure
the device is not shut down or losing power during this step!
6. Close the firmware update utility.
7. Turn the quTAU device off (and possibly on again). If you don’t do this, the old
firmware will still be in effect until the next restart.
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