Narrative:

During this session at R40 traffic volume and complexity were high. We were responsible for 15-20 aircraft. Aircraft X was in level flight at FL250 diverging north at ZZZ from aircraft Y who checked in level at FL230 and was diverging east at ZZZ. I issued climb clearance to aircraft Y on initial check in through aircraft X. When conflict alert activated I amended aircraft Y's altitude to FL240 and the pilot said they were just passing through it. I was asked what I wanted them to do and I told them to descend back to FL240. I saw no reason to turn either aircraft as both were diverging would be separated within two updates.standard separation was lost at 2.64 miles and 900ft. They were 4.14 miles and zero feet before achieving lateral divergence. I accept full responsibility for this error. Primary contributing factors were data block congestion and a close in scan failure. In total there were six aircraft within 12 miles of ZZZ. I just missed one.conflict alert parameters could be increased to account for aircraft performance possibilities. These aircraft were two thousand feet apart and diverging in two minutes. Had conflict alert activated immediately after removing the temporary altitude this error could have been prevented. Two minutes and two thousand feet isn't outside the realm of possibility for most aircraft.

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Original NASA ASRS Text

Title: Center Controller describes a loss of separation with two aircraft he was working. Numerous aircraft in the vicinity with data block congestion. Controller had separation; but elected to climb traffic through a diverging aircraft; having less than 5 miles. Another Controller reports that the working Controller is dangerous and puts aircraft in unsafe situations and watches.

Narrative: During this session at R40 traffic volume and complexity were high. We were responsible for 15-20 aircraft. Aircraft X was in level flight at FL250 diverging North at ZZZ from Aircraft Y who checked in level at FL230 and was diverging east at ZZZ. I issued climb clearance to Aircraft Y on initial check in through Aircraft X. When conflict alert activated I amended Aircraft Y's altitude to FL240 and the pilot said they were just passing through it. I was asked what I wanted them to do and I told them to descend back to FL240. I saw no reason to turn either aircraft as both were diverging would be separated within two updates.Standard separation was lost at 2.64 miles and 900ft. They were 4.14 miles and zero feet before achieving lateral divergence. I accept full responsibility for this error. Primary contributing factors were data block congestion and a close in scan failure. In total there were six aircraft within 12 miles of ZZZ. I just missed one.Conflict alert parameters could be increased to account for aircraft performance possibilities. These aircraft were two thousand feet apart and diverging in two minutes. Had conflict alert activated immediately after removing the temporary altitude this error could have been prevented. Two minutes and two thousand feet isn't outside the realm of possibility for most aircraft.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.