Users of the laboratory must have successfully completed the "Radiation Safety Refresher Training for X-ray Users" course as a prerequisite to conduct X-ray diffraction measurements in the laboratory. This course is on-line, can be found at http://www.ors.od.nih.gov/ds/rsb/training/xray/ At the end of the course a certificate is offered, users are required to present a copy of this certificate to the X-ray diffraction facility supervisor to gain access.

            Users can sign up for any future date to collect data for a maximum duration of 4 consecutive days. A "data collection day" starts at 10am and ends also at 10am. Users can sign up for multiple times as long as no single period exceeds 4 days. Users can sign up for more than one detector if they wish, but two sign up periods on different detectors cannot overlap. When collecting data, users can extend their 4 days period on the detector they are using provided that no other user has signed up for the following days at 5pm of the third day of the current period. In exceptional circumstances, such as anomalous data collection in low symmetry space groups, or an upcoming synchrotron trip with extensive screening requirements, users can request longer sign up periods. These requests are evaluated on an individual basis and by discussions between the user, his or her group leader and the facility manager. In general these requests will be accommodated, but only after taking the current load on the facility and its operational status into consideration. The name and access information (e-mail, phone number) of any user, who is conducting an active experiment must be displayed on calendars mounted on the door of the laboratory, even if the original sign up was done electronically. Ongoing experiments with no user name and access information displayed will be terminated. Users are required to notify all other users if they decide to cancel their sign-ups or they terminate their experiments early.
           
            Users are allowed to enter the walk-in style radiation safety enclosure only when the X-ray shutter is closed, and only to either mount or to remove their samples or to change the X-ray generator power setting, or to adjust the sample-to-detector distance or to operate the cryo system. Users are not allowed to change or adjust the collimators or the X-ray optics. At all other times, the walk-in style radiation safety enclosure must be closed and no user can be inside of the enclosure. After closing the enclosure doors, the interlock has to be activated by entering 0000# on the keypad mounted on the enclosure. Successful activation is indicated by a permanent green light on the keypad box, without this indication the shutter will not open. The interlock has to be reactivated after each opening the enclosure doors, but only after all doors have been closed again. Failure to act according to these restrictions, or any attempt the defeat the interlock system will result in an immediate withdrawal of  the  privileges to conduct measurements in the laboratory.

            Users must be trained in basic experimental crystallographic procedures such as sample mounting and removal, optical centering, and the operation of the software system that controls the data collection instrument. They must be able to make reasonable decisions regarding the parameters of their experiments. It is the responsibility of the user's group leader to provide such training or to assure that such training has been provided. While the facility supervisor should provide reasonable help in such training, it is the group leader who is ultimately responsible for the qualifications, competence and safety awareness of their trainees.   
           
            All experiments are conducted at the standard setting of 40kV and 30mA X-ray generator power settings on the A and B systems, while the standard setting on the C system is 50kV and 100mA.  Settings higher than this (either in voltage or in current) are forbidden as they will result in permanent damage to the instrumentation. At the start of an experiment, the  user may have to increase the settings if they are lower than the standard setting applicable to the particular generator. This is achieved by first increasing the voltage in steps up to the limit of 40kV, (50kV on the C generator) and then by increasing the current in steps of up to 30mA. (to 100mA on the C generator) The current increase must be done slowly, typically not faster than 10mA every 2 minutes. It is important to make sure that the generator vacuum does not exceed the 110 mV reading on the ion-gauge display.

            When mounting crystals, it is important to loosen the set-screw on the goniostat to allow vertical movement that is needed for proper centering. When the appropriate height is achieved, this screw should be tightened before the final horizontal centering using the goniometer head adjustments can proceed. It is very important to avoid touching either the collimator or the beamstop during this process as misalignment any of these will result in seriously compromised data quality and may result in excess radiation escaping. 

            At the end of the experiment, the generator power must be lowered to the stand-by level of 20kV and 10mA. This is achieved by first lowering the current in steps to 10mA, and then lowering the voltage down to 20kV. Lowering the X-ray generator power can be done relatively quickly, but it is important to lower the current first.

            Data collected in the laboratory has to be backed up on the user's computer as soon as possible after the end of the experiments. Data older then two calendar weeks can be deleted by anybody without asking questions first. On the other hand it is strictly prohibited to delete of other user's data if the data is less than two weeks old.

            Liquid Nitrogen dewars cannot be left on the X-ray generators, as condensation will result in an immediate electrical hazard. As the generators operate at 50,000 V, the consequences would be obviously serious. User are required to assure that adequate amounts of liquid Nitrogen is available for their experiments. A wrench located behind the brown tool box can be used to connect and disconnect tanks. The wrench has to be placed back to the same place after use. All work in the X-ray laboratory with cryogenic liquids require the use of adequate protective devices such as gloves and safety glasses. Without these, cryogenic liquids can not be used in the laboratory. Empty tanks can be refilled on the first floor (near the loading dock) of building 5. Keep in mind that that it takes about 8 hours after filling that sufficient pressure builds up in the tanks, therefore they cannot be used right after filling.

            All of the X-ray generators are equipped with sirens to warn users of unusual operating conditions that may present either radiological, electrical or mechanical dangers to the users. If any of the sirens are on, users must leave the laboratory immediately and notify the laboratory supervisor at the emergency contact numbers located on the outside of the laboratory door. Also, any unusual sound, fluid or gas discharge must be interpreted as an unusual operating condition that indicates a potentially dangerous situation developing. Again, users must leave the laboratory immediately.