## 3 Results
### In Situ Dynamic Light Scattering
#### 3.2.1 DLS Setup  
Similar to the setup developed by [PERSON] et al. [12], the DLS setup using the KWS-2 is built modularly, consisting of five major components: light source, optics defining the scattering geometry, detector, correlator, and computer. The optics defining the scattering geometry are placed at the sample position on the instrument, whereas the other components are mobile connected with optical fibers (Figure 8). The light from a He-Ne laser (20 mW, 632.8 nm) is coupled to a fiber (Schafter + Kirchhoff GmbH, Hamburg, Germany) and brought to the neutron instrument. A collimator (Schafter + Kirchhoff GmbH, Hamburg, Germany) and a mirror focus the light from the fiber into the center of the quartz cell, which was previously aligned in the center of the neutron beam. The scattered light under the angle \(\vartheta\) (in the present case \(\vartheta=120^{\circ}\)) is then guided by a mirror and collimated into a second fiber. The optics are mounted using standard optic holders (Thorlabs) and placed on a platform anchored on the vacuum tank of the neutron detector. This concept allows the use of a variety of sample changers with the existing optics. For alignment purposes, one can mark a spot on the quartz cuvette in the sample holder, where the laser hits the cell surface. After disconnecting the laser fiber and reconnecting it to the collimator for the scattered light, one can see and align the light path for the scattered light to the same sample spot marked in the quartz cell. This alignment is often good enough to obtain a first correlation curve which can then be optimized to a better intercept using nanoparticle solutions as highly scattering test samples. This alignment concept relies on the fact that both the laser light and the scattered light are guided through a single mode optical fiber, a specialty of this realization of in situ DLS.  
After passing the mirror, the collimator, and the single mode fiber, the scattered photons arrive at an APD detector (Excelitas Technologies Corp. SPCM-AQRH-FC, Waltham, MA, USA). The recorded electrical pulses are autocorrelated with an ALV-7004 Multiple Tau Digital Correlator (ALV-GmbH, Langen, Germany). A computer displays the measured intensities and the autocorrelation functions. The correlation function and the recorded intensities are saved for further analysis. To protect the detection components, a filter wheel with neutral density filters is placed before coupling the laser light into the fiber.  
Figure 8: **Left**: Schematic view of the setup for simultaneous DLS and SANS analysis of samples using the KWS-2. **Right**: view of the setup on the sample stage of the neutron SANS diffractometer, between the sample aperture of the collimation system and the entrance window of the evacuated detector tank. Light beam trajectories to and from the sample are indicated in red. The sample cuvettes are placed in the locations of a Peltier-based multi-position variable temperature holder (Quantum Northwest Inc., Liberty Lake, WA, USA) that can move each sample in neutron/light beams in a controlled way.  
Based on the photon counts detected for each sample, the wheel adjusts to the optimum filter for each measurement.  
A DLS measurement begins shortly after the start of the neutron measurement, which has been triggered by the instrument control software NICOS. Light scattering data are recorded in parallel and saved on a separate computer with a unique identifier containing the run number of the neutron measurement. The correlator determines the normalized intensity-intensity (second-order) auto-correlation function g\({}^{\text{II}}(\tau)\). Data processing is performed post-experiment, by obtaining the electrical field first-order correlation function g\({}^{\text{I}}(\tau)\) from g\({}^{\text{II}}(\tau)\), according to the Siegert relation. g\({}^{\text{I}}(\tau)\) is interpreted using a triple-exponential fit, corresponding to a triple-modal distribution [38]. For samples with higher polydispersity, a CONTIN fit routine can be used [39].