## 2 Time Resolution
See Figure 1[7]. One may get the impression that every 10 years one gains a factor of 10 in time-resolution, but in reality, it demonstrates how strongly time resolution depends on the system being studied. Even though progress in instrumentation has been considerable, the quality of samples, to a great extent, still determines the achievable time-resolution. For example, in the case of a lysozyme crystallization experiment car  
Figure 1: Time-resolved SANS data from the surfactant templated formation of mesoporous silica nanoparticles. This is one of the fastest neutron scattering experiments reported so far. A time-resolution of 10 s/frame rendered analyzable data (reproduced with permission from [7], American Chemical Society, 2012). resolution of hours/frame was mentioned [8]. Similarly, 10 min/frame was reported for the growth kinetics of lipid-based nano-discs to unilamellar vesicles [9]. When not making full use of selective deuteration, one can still expect 20 min/frame of low statistical data quality in a demixing experiment of incompatible crude oils [10]. Improving the achievable time resolution by increasing the neutron flux is a very expensive process. The European Spallation Source (ESS) being constructed in Lund, Sweden and the proposed Second Target Station (STS) of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory in the USA will be the next generation of neutron sources offering increased neutron fluxes. However, both will require some years and large budgets until they are completed and ready for experiments. In the meantime, there are experimental methods currently available that significantly improve time-resolved experiments. For experiments where cycling is an integral part of the study (i.e., oscillatory shear), or the periodic deformation used in simulations of the behavior of rubber tires, one can use a series of repeated short time frames and then merge the data series on-line. In principle, if the sample survives, one can collect for extended periods of time to obtain the required statistics and thus obtain a very high time-resolution. This method has been used for large oscillatory shear measurements (LAOS) on triblock copolymer micelles [11] and the effects of start-up and cessation of flow [12] using a commercial stress-controlled rheometer in the Couette geometry, where the rheometer generates an analog I/O signal that can be used to synchronize with the neutron scattering data acquisition system. In the case of the these strongly scattering systems, 300 cycles were sufficient to achieve 100 ms time-resolved data. If an experiment that is not intrinsically cyclic can be accurately repeated, then one can follow the same procedure. Such a strategy can work if the sample can be recycled or if the synthesis/preparation is not too costly or time-consuming. Whether this is practically feasible depends on the length of the interval between experiments. In a temperature quench or pressure jump experiment, the dead time would be the required time to heat the sample up again before the next quench or to release/built up the pressure. A recent example of this is a series of pressure jumps that were used to study the phase transition kinetics of smart N-n-propylacrylamide microgels [13]. The jumps (200-40-200 bar) were performed with a frequency of approximately 23 Hz and repeated 5400 times. A time-resolution of 10 ms/frame was obtained (2 Hz frequency) over a period of 1.5 h of experimentation. Another approach used to obtain good quality time resolution data of a continuous process is to translate the distance from the point where the perturbation takes place (e.g., mixing, extrusion, temperature change) to the point where the neutron beam interacts with the sample and translating this into time. By varying the time between the initiation point and the beam intercept, one can construct a timeline. An excellent example of this method is the (X-ray) study of polyolefin crystallization using an extruder [14]. Such experiments could easily be used on neutron beamlines as well.