## 3 Sample Environments
### Temperature  
Temperature is one of the basic parameters that can be varied during an experiment. This was already remarked upon by [PERSON] in the proceedings of the first small angle scattering conference organized in 1965 [19]. For soft matter, research temperature control is important since the thermal history of a sample can dictate the material's ultimate properties. The main technical issue for neutron scattering is that neutron beam sizes are relatively large, making it more difficult to minimize sample environment temperature gradients. In the case of sample environments for static experiments, there are good commercial solutions to this problem. However, when there are special requirements, like the need to rotate the sample during a crystallization experiment, where the possibility of sedimentation is a real possibility, temperature control becomes somewhat more complicated, but in the range of between \(-10\) and \(80\)\({}^{\circ}\)C, there are solutions [20; 21]. In these cases, temperature control can be achieved using halogen light bulbs as the heating source and an infra-red sensor as thermal sensor, with an accuracy of approximately \(\pm 2\)\({}^{\circ}\)C. Also, accurate control can be achieved by using water baths.  
For soft matter, however, the sample's thermal history can determine its final morphology and it is thus important to accurately control both heating and, especially, cooling rates. As such, a logical development is to combine neutron scattering with differential scanning calorimetry (DSC), a development that was implemented at X-ray facilities in 1995 [22; 23]. The engineering difficulties due to the requirement to have access to the sample with larger neutron beams is evident since it took until 2014 before this was implemented on neutron beamlines [24] with an instrument that can operate in the temperature range \(-150\)\({}^{\circ}\)C to \(500\)\({}^{\circ}\)C.  
The larger beam size also implies that for time-resolved experiments involving temperature jumps, the situation is more complicated due to the low thermal conductivity of the samples. Fast quench rates, combined with the larger sample sizes required for neutron experiments, increases the problem of thermal gradients over the sample so that one does not obtain a realistic correlation between temperature and structure at a given temperature, but over a bandwidth of temperatures. However, compared to X-rays, there is the advantage that metallic window materials can be used which, when connected with the heating/cooling elements, can mitigate the gradient problem to some degree.  
For jumps at higher temperatures, one could contemplate the use of microwave radiation [25], which can provide more uniform heating of the sample. However, for quenches to a lower temperature, material thermal conductivity remains the rate-limiting parameter. For liquids, one can perform temperature jump (T-jump) experiments by injecting the fluid into a pre-heated/cooled cell using, for instance, a syringe pump [26]. A temperature jump device specifically designed to operate on a SANS beamline, using two furnaces between which the sample is shuttled, can operate in the range 150-600 K with heating rates up to 19 K/s and cooling rates 11 K/s [27]. One can also adapt a stop-flow cell to operate as a T-jump device. This was done to understand the kinetics of the collapse, transition, and subsequent cluster formation in a micellar solution of P(S-b-NIPAM-b-S) [28]. See Figure 3. Approximately 100 s were required for a modest temperature jump of \(6\)\({}^{\circ}\)C.  
The latter example shows that it is not always necessary to use world record T-jump speeds to obtain the desired information with respect to the scientific question to be answered.