Photomultiplier tubes output a small amount of current even when operated in a completely dark state. This output is called the dark current and the resultant noise is an important factor in determining the lower detection limit. The above graph shows typical dark currents from micro PMTs.
Photomultiplier tubes have a fast time response and can capture very short events. The above graph shows a typical output waveform when a light pulse with a width of 70 ps is input to a micro PMT.
The time interval between the arrival of light at the photocathode and the instant when the anode output current reaches its peak amplitude is called the electron transit time. The transit time spread usually called T.T.S., indicates fluctuations in the electron transit time measured when the photocathode is fully illuminated with single photons and is defined as the FWHM (full width at half maximum) of the fluctuations in the histogram.
An intense light pulse input to the photocathode causes a large current to flow in the latter dynode stages that induces current saturation. This causes the output current to deviate from its ideal linearity. The above graph shows pulse linearity characteristics of micro PMTs.
Ripple noise is caused by the electronic oscillator of the built-in power supply. This noise signal can be observed on an oscilloscope along the baseline in a low voltage range by feeding the output signal to the oscilloscope while no light is incident on the micro PMT.
This uniformity is the variation in sensitivity relative to the incident light position on the photocathode. The above graph shows an example of anode output measured by scanning a 1 mm diameter light spot over the photocathode surface of a micro PMT at a pitch of 0.1 mm in the X and Y axis directions.
The anode sensitivity of photomultiplier tubes is affected by the ambient temperature. Temperature characteristics for anode sensitivity are wavelength-dependent and the temperature coefficient generally changes from a negative value to a positive value near the long wavelength limit. The above graph shows temperature coefficient data for each photocathode.
An external magnetic field causes photoelectrons in a photomultiplier tube to deviate from their normal trajectories, causing a loss of gain. The extent of the loss of gain depends on the direction of the magnetic field. The above graph shows effects from magnetic fields on the output of a micro PMT, indicating that the magnetic field in the Z direction has the largest effect on the output.
Some dark current pulses are generated in a photomultiplier tube during operation even if no light is incident on it.
Dark count is the number of dark current pulses per second (s-1) and indicates the approximate lower limit of signal detection.
When light is randomly incident on a photomultiplier tube, the output pulses begin to overlap each other as the light level increases and the count value is no longer proportional to the light level. If the incident light level greatly exceeds the count linearity, a signal is output to indicate an excessive light input.
When the number of measured pulses exceeds 106 s-1, counting errors start to appear due to pulse overlap. One method for improving the count linearity utilizes a correction formula to find the approximate values. The above graph shows improved count linearity characteristics obtained by applying this correction formula.
It looks like you're in the . If this is not your location, please select the correct region or country below.
You're headed to Hamamatsu Photonics website for JP (English). If you want to view an other country's site, the optimized information will be provided by selecting options below.
For modern websites to work according to visitor’s expectations, they need to collect certain basic information about visitors. To do this, a site will create small text files which are placed on visitor’s devices (computer or mobile) - these files are known as cookies when you access a website. Cookies are used in order to make websites function and work efficiently. Cookies are uniquely assigned to each visitor and can only be read by a web server in the domain that issued the cookie to the visitor. Cookies cannot be used to run programs or deliver viruses to a visitor’s device.
Cookies do various jobs which make the visitor’s experience of the internet much smoother and more interactive. For instance, cookies are used to remember the visitor’s preferences on sites they visit often, to remember language preference and to help navigate between pages more efficiently. Much, though not all, of the data collected is anonymous, though some of it is designed to detect browsing patterns and approximate geographical location to improve the visitor experience.
Certain type of cookies may require the data subject’s consent before storing them on the computer.
This website uses two types of cookies:
There are two ways to manage cookie preferences.
If you wish to restrict or block web browser cookies which are set on your device then you can do this through your browser settings; the Help function within your browser should tell you how. Alternatively, you may wish to visit www.aboutcookies.org, which contains comprehensive information on how to do this on a wide variety of desktop browsers.
Occasionally, we may use internet tags (also known as action tags, single-pixel GIFs, clear GIFs, invisible GIFs and 1-by-1 GIFs) at this site and may deploy these tags/cookies through a third-party advertising partner or a web analytical service partner which may be located and store the respective information (including your IP-address) in a foreign country. These tags/cookies are placed on both online advertisements that bring users to this site and on different pages of this site. We use this technology to measure the visitors' responses to our sites and the effectiveness of our advertising campaigns (including how many times a page is opened and which information is consulted) as well as to evaluate your use of this website. The third-party partner or the web analytical service partner may be able to collect data about visitors to our and other sites because of these internet tags/cookies, may compose reports regarding the website’s activity for us and may provide further services which are related to the use of the website and the internet. They may provide such information to other parties if there is a legal requirement that they do so, or if they hire the other parties to process information on their behalf.
If you would like more information about web tags and cookies associated with on-line advertising or to opt-out of third-party collection of this information, please visit the Network Advertising Initiative website http://www.networkadvertising.org.
We use third-party cookies (such as Google Analytics) to track visitors on our website, to get reports about how visitors use the website and to inform, optimize and serve ads based on someone's past visits to our website.
You may opt-out of Google Analytics cookies by the websites provided by Google:
We inform you that in such case you will not be able to wholly use all functions of our website.