## 1 Introduction  
In the past ten years, there has been a considerable number of studies performed investigating repetitively non-chain pulsed HF/DF lasers because of their advantages of high output power, special infrared output band, compact and simple structure, and safe operation [1; 2; 3; 4; 5; 6; 7]. These advantages make lasers of this type promising for applications in many fields such as spectroscopy, laser radar transmitters, laser ranging, atmospheric monitoring, military, etc. [8; 9; 10; 11; 12; 13; 14]. Besides, non-chain short-pulsed HF/DF lasers comprise an ideal pump source for novel Fe:ZnSe lasers, the fluorescent lifetimes of which are 360 ns at \(T\) = 292 K, and this process can expand the laser spectrum to 4-5 \(\upmu\)m [15; 16; 17; 18]. In the past few years, most studies have focused on the achievement of high radiation energies (powers), high electric efficiency, and repetition rates in non-chain HF/DF lasers. The radiation energy up to 325 J at the electric efficiency of 3.4% was achieved in an electric discharged non-chain DF laser by applying self-initiated volume discharge in a SF\({}_{6}\)-D\({}_{2}\) gas mixture [19]. This energy was achieved with a discharge gap \(d\) = 27 cm and it is the highest energy for non-chain DF lasers reported so far. A further increase of the generation energy of HF (DF) non-chain lasers to 1 kJ can be achieved by increasing the separation \(d\) between electrodes and the transversal dimension of the cathode, but this has very high power supply requirements. In Ref. [20], after optimizing the mixture composition, specific input energy, and uniformity of electric field, the highest electrical efficiency of 6.4% reported until now for non-chain DF lasers with electric discharge was attained by [PERSON], and the output energy was more than 1 J. In Ref. [21], a 1 kHz high-repetition-rate non-chain HF/DF laser with an average laser output power of up to 2.5 W in SF\({}_{6}\)-D\({}_{2}\) gas mixture was achieved by [PERSON]. A 2.2 kHz repetition rate atmospheric pressure HF/DF laser with an output power of 33 W and electrical efficiency of 1.6% was obtained by [PERSON]; the electric discharge was matched by diluting helium in the working mixture to preserve the discharge conditions [22]. Applying three electric-discharge laser modules of the same type, a non-chain DF laser with 400 W output power at a pulse repetition rate of 10 Hz was obtained after optimizing the cavity Q-factor, the composition, and the total pressure of the working mixture [23]. A closed-cycle, repetitively pulsed HF laser with an output power of 55 W at 100 Hz was presented by optimizing gas flow velocity, performing a small replenishment of the working gas, and applying a 3A molecular sieve in the discharge chamber [24]. Although energy (power) is an important indicator for evaluating a laser's performance, many applications for mid-infrared lasers require not only high energy strength in emission, but also good beam quality. Stable resonator HF/DF lasers can easily achieve high output power and are simple to install and adjust, but the far-field divergence angle is relatively large compared with unstable resonator lasers. When the laser is transmitted for a certain distance, the laser beam spreads rapidly and its energy density decreases significantly, which limits the long-distance applications of stable repetitively pulsed HF/DF lasers. In remote atmosphere ecological monitoring, the laser beam needs to travel a distance of more than 10 km to detect air contaminants such as gaseous hydrocarbons, HCI, N\({}_{2}\)O, and SO\({}_{2}\), so compressing the beam divergence is essential. However, the beam quality of non-chain pulsed HF/DF lasers has not yet been investigated sufficiently thoroughly. There are only a few papers which briefly introduce the results of divergence measurements. In Ref.