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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7 SOFTWARE
7 Software
Software for the most common tasks is already provided by qutools GmbH. Here, we only
take a quick look at these solutions and their advantages. A more thorough explanation
will follow in the description of the different tasks.
Figure 6: Software concept of the quTAU. The quTAU device is connected via USB2.0
with the PC. Except the Daisy GUI, all applications are using the DLL tdcbase.dll to
communicate with the device driver.
7.1 Concept
The quTAU software concept is depicted in Figure 6. The device is connected via USB2.0,
so the first piece of software handling it on the PC side is the USB device driver. The
device driver then talks to directly to one (!) of the client programs, so either to the
daisy GUI client or to the user DLL. The DLL then communicates with the command
line interface, the quTAU GUI, LabVIEWTM VIs or other user written programs.
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7 SOFTWARE
7.2 Daisy
The native GUI Daisy is now mostly obsolete, since practically all features are also avail-
able in the new LabVIEWTM based quTAU GUI. It is still included in this software
package, but will be no longer maintained from now on. It does not use the tdcbase.dll
DLL. The opening screen is shown in Figure 7, the different features are simply accessed
by clicking on the different tabs. Double-clicking a tab decouples it from the main window,
making it possible to view multiple tabs at once.
Figure 7: The opening screen of the Daisy GUI. Different tasks can be accessed by the
different tabs at the top. Please note that this window will display additional options for
upgraded quTAU devices, so the appearance varies depending on the used device.
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7 SOFTWARE
7.3 quTAU GUI
The quTAU GUI is designed to easily perform the most common tasks like showing
the count rate and coincidence rate trend for each channel, saving timestamps to a file,
and displaying different histograms like start-(multi)stop histograms or cross correlation
histograms (g(2) functions). The opening screen is shown in Figure 8. A convenient menu
and the different tabs allow a self-explanatory usage of the program.
Figure 8: The opening screen of 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. A status bar
(3) at the bottom shows additional information and the state of software and device.
7.4 Command Line Interface
The command line interface can be used for some simple tasks as a one-time readout of the
count rates, writing time stamps to a file or saving histogram data. It is mostly intended
as an example, though. To use it, open a Windows command prompt (Press ”Start”, type
”cmd” and press Enter), go to the directory userlib/daisy/ and call tdccli(.exe). Use
the parameter -h for additional information.
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7 SOFTWARE
7.5 Using the quTAU with your own software (Library func-
tions)
In order to enable customers to write their own software for using the time-to-digital
converter quTAU, qutools GmbH provides a DLL containing all functions needed to com-
municate with the device. For use with LabVIEWTM, a wrapper VI is provided for each
of these functions (userlib/labviewXX/lowlevelvis). Please note that the name of the
VI is equal to the DLL function name. Examples in C (userlib/src) and LabVIEWTM
(userlib/labviewXX/examples) show how parts of a program might look like.
7.5.1 The qutools tdcbase.dll DLL/lib
The DLL tdcbase.dll is provided by qutools GmbH to enable customers to use the time
to digital converter quTAU in their own software projects. It is available for MS Windows
as well as for Linux and in versions for 32 bit and 64 bit architectures. You can download
the latest version from the qutools homepage. It is also used by both the LabVIEWTM
application and the command line interface, see above.
A complete list of all functions the DLL provides and information about how to call these
functions is included as doxygen generated documentation in userlib/doc/index.html.
Additionally, there will be examples of how to combine the functions to achieve a certain
task. To visualize this, simplified LabVIEWTM block diagrams will be used. Please
remember that the (shown) names of the used VIs are equal to the DLL function names.
7.5.2 LabVIEWTM Integration
For integration of the quTAU in LabVIEWTM using the DLL, wrapper VIs are provided
at /userlib/labviewXX/lowlevelvis/. Each of these low level VIs can be used to call
the respective DLL function. When using the low level VIs, the following facts are helpful
to know:
1. The DLL file tdcbase.dll must be found by the LabVIEWTM program. For this
purpose, the first DLL call triggers a search for the DLL file. It is expected in the
application directory or any of its parents. Additionally, it can be placed in a sub
folder lib,lib32 or lib64. If the DLL is not found, the user is prompted to provide
the path. In order to avoid this prompt, please place the DLL as described.
2. All low level VIs have error in- and outputs. This is convenient to determine their
temporal sequence by wiring the error line from one to the next. It is important to
understand that the VIs are designed to do nothing in case they are called already
with an error. The error output contains the return code as well as the corresponding
error message.
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7 SOFTWARE
7.5.3 Device Initialization
In order to communicate with the quTAU device, the DLL has first to be initialized using
TDC init. In case the device is not found or available, the init function returns the error
code ”2”: ”No connection was established”. Nevertheless, the DLL will still be initialized
in DEMO mode. This allows for testing and offline use of the DLL functions. On Labview,
make sure to catch this error, otherwise all subsequent DLL calls will not be executed.
An example is shown in figure 9.
Figure 9: Initialization, see example demo mode.vi. The return code ”2” signals ”No
connection was established” and the DLL automatically switches to demo mode.
Necessary functions for the device initialization:
tdcbase.h:
int TDC init (int deviceId)
Additional functions related to the device initialization:
tdcbase.h:
double TDC getVersion ()
const char ∗TDC perror (int rc)
double TDC getTimebase ()
TDC DevType TDC getDevType ()
Bln32 TDC checkFeatureHbt ()
Bln32 TDC checkFeatureLifeTime ()
int TDC enableChannels (Int32 channelMask)
7.5.4 Device Deinitialization
Please make sure TDC deInit is always called at the end of your programs. This is
necessary to terminate the device properly and to enable a reinitialization for the next
program start.
Table 2: Examples: Device Initialization
LabView Example /userlib/labviewXX/examples/demo mode.vi
C Example -
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7 SOFTWARE
Necessary functions for the device DE-initialization:
tdcbase.h:
int TDC deInit ()
Additional functions related to the device DE-initialization:
tdchbt.h:
void TDC releaseHbtFunction (TDC HbtFunction ∗fct)
tdclifetime.h:
void TDC releaseLftFunction (TDC LftFunction ∗fct)
Table 3: Examples: Device Deinitialization
LabView Example /userlib/labviewXX/examples/demo mode.vi
C Example -
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8 INPUT PARAMETER SETTINGS
8 Input Parameter Settings
You might want to change the default configuration of the digital inputs, like the trigger
level, termination, or rising/falling edge selection of the input channels. Depending on
your device (with or without hardware extension) not all options might be available.
Table 4gives an overview.
Table 4: Digital input configuring. Available features of the different models.
quTAU quTAU (H)
trigger level fixed adjustable per channel
50 Ω termination on/off globally per channel
rising/falling edge selection - per channel
channel delay - per channel
•Trigger level: necessary threshold voltage to trigger an event.
•Termination: switches the termination of the input channels between 50 Ω and 5 kΩ.
•Edge selection: determines whether the event is triggered at the rising or the falling
edge of a signal exceeding the voltage threshold.
•Channel delay: Sets additional delays for the input channels. Please note that this
currently doesn’t influence coincidence counting. It affects all histograms, though.
Please note that these settings are saved in the device and therefore persistent over the
different software realizations. A restart of the device, however, will reset all settings to
the default state.
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8 INPUT PARAMETER SETTINGS
8.1 Software Realizations
Input parameters can be set in the Daisy GUI as well as in the quTAU GUI. There are
some presets available in both cases, to quickly change all parameters to commonly used
values.
8.1.1 Daisy
All settings can be accessed in the ”Detector Parameters” tab, see Figure 10.
Figure 10: Settings in he Daisy GUI. The channel input settings can be changed via the
controls in the highlighted area. Please note that appearance of this window may change
depending on the used hardware; here, a quTAU (H) is used.
8.1.2 quTAU GUI
Simply click Settings->Input Settings... in the menu bar to display a dialog con-
taining control elements for all available input settings, see Figure 11. Changes take
immediate effect, you don’t have to close the window.
8.2 DLL Usage
A minimal working example is provided as configure IO.vi (see figure 12).
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8 INPUT PARAMETER SETTINGS
Usage examples are also available in the src folder as example[1,3,5].c.
Functions relevant to the signal conditioning:
tdcbase.h:
TDC DevType TDC getDevType ()
int TDC configureSignalConditioning (Int32 channel, TDC SignalCond
conditioning, Bln32 edge, Bln32 term, double threshold)
int TDC getSignalConditioning (Int32 channel, Bln32 ∗on, Bln32 ∗edge,
Bln32 ∗term, double ∗threshold)
int TDC configureSyncDivider (Int32 divider, Bln32 reconstruct)
int TDC getSyncDivider (Int32 ∗divider, Bln32 ∗reconstruct)
int TDC enableChannels (Int32 channelMask)
int TDC setChannelDelays (const Int32 ∗delays)
int TDC getChannelDelays (Int32 ∗delays)
int TDC switchTermination (Bln32 on)
int TDC enableTdcInput (Bln32 enable)
Figure 11: The input settings dialog of the quTAU GUI.
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8 INPUT PARAMETER SETTINGS
Table 5: Examples: Configure Input Parameter Settings
LabView Example /userlib/labviewXX/examples/configure IO.vi
C Example /userlib/src/example[1,3,5].c
Figure 12: Digital Input configuration, see example configure IO.vi. Please note that
the logic level settings are set per channel and the channel delays as a set of eight.
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